Bibliografie tematiche / Polycomb complex

Letteratura scientifica selezionata sul tema "Polycomb complex"

Autore: Grafiati
Pubblicato: 31 agosto 2024

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Articoli di riviste sul tema "Polycomb complex"

1

Strutt, H., e R. Paro. "The polycomb group protein complex of Drosophila melanogaster has different compositions at different target genes." Molecular and Cellular Biology 17, n. 12 (dicembre 1997): 6773–83. http://dx.doi.org/10.1128/mcb.17.12.6773.

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Abstract (sommario):
In Drosophila the Polycomb group genes are required for the long-term maintenance of the repressed state of many developmental regulatory genes. Their gene products are thought to function in a common multimeric complex that associates with Polycomb group response elements (PREs) in target genes and regulates higher-order chromatin structure. We show that the chromodomain of Polycomb is necessary for protein-protein interactions within a Polycomb-Polyhomeotic complex. In addition, Posterior Sex Combs protein coimmunoprecipitates Polycomb and Polyhomeotic, indicating that they are members of a common multimeric protein complex. Immunoprecipitation experiments using in vivo cross-linked chromatin indicate that these three Polycomb group proteins are associated with identical regulatory elements of the selector gene engrailed in tissue culture cells. Polycomb, Polyhomeotic, and Posterior Sex Combs are, however, differentially distributed on regulatory sequences of the engrailed-related gene invected. This suggests that there may be multiple different Polycomb group protein complexes which function at different target sites. Furthermore, Polyhomeotic and Posterior Sex Combs are also associated with expressed genes. Polyhomeotic and Posterior Sex Combs may participate in a more general transcriptional mechanism that causes modulated gene repression, whereas the inclusion of Polycomb protein in the complex at PREs leads to stable silencing.
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2

Chiang, A., M. B. O'Connor, R. Paro, J. Simon e W. Bender. "Discrete Polycomb-binding sites in each parasegmental domain of the bithorax complex". Development 121, n. 6 (1 giugno 1995): 1681–89. http://dx.doi.org/10.1242/dev.121.6.1681.

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Abstract (sommario):
The Polycomb protein of Drosophila melanogaster maintains the segmental expression limits of the homeotic genes in the bithorax complex. Polycomb-binding sites within the bithorax complex were mapped by immunostaining of salivary gland polytene chromosomes. Polycomb bound to four DNA fragments, one in each of four successive parasegmental regulatory regions. These fragments correspond exactly to the ones that can maintain segmentally limited expression of a lacZ reporter gene. Thus, Polycomb acts directly on discrete multiple sites in bithorax regulatory DNA. Constructs combining fragments from different regulatory regions demonstrate that Polycomb-dependent maintenance elements can act on multiple pattern initiation elements, and that maintenance elements can work together. The cooperative action of maintenance elements may motivate the linear order of the bithorax complex.
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3

De, Sandip, Natalie D. Gehred, Miki Fujioka, Fountane W. Chan, James B. Jaynes e Judith A. Kassis. "Defining the Boundaries of Polycomb Domains in Drosophila". Genetics 216, n. 3 (18 settembre 2020): 689–700. http://dx.doi.org/10.1534/genetics.120.303642.

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Abstract (sommario):
Polycomb group (PcG) proteins are an important group of transcriptional repressors that act by modifying chromatin. PcG target genes are covered by the repressive chromatin mark H3K27me3. Polycomb repressive complex 2 (PRC2) is a multiprotein complex that is responsible for generating H3K27me3. In Drosophila, PRC2 is recruited by Polycomb Response Elements (PREs) and then trimethylates flanking nucleosomes, spreading the H3K27me3 mark over large regions of the genome, the “Polycomb domains.” What defines the boundary of a Polycomb domain? There is experimental evidence that insulators, PolII, and active transcription can all form the boundaries of Polycomb domains. Here we divide the boundaries of larval Polycomb domains into six different categories. In one category, genes are transcribed toward the Polycomb domain, where active transcription is thought to stop the spreading of H3K27me3. In agreement with this, we show that introducing a transcriptional terminator into such a transcription unit causes an extension of the Polycomb domain. Additional data suggest that active transcription of a boundary gene may restrict the range of enhancer activity of a Polycomb-regulated gene.
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4

Seong, Ihn Sik, Juliana M. Woda, Ji-Joon Song, Alejandro Lloret, Priyanka D. Abeyrathne, Caroline J. Woo, Gillian Gregory et al. "Huntingtin facilitates polycomb repressive complex 2". Human Molecular Genetics 19, n. 4 (23 novembre 2009): 573–83. http://dx.doi.org/10.1093/hmg/ddp524.

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5

Mohd-Sarip, Adone, Jan A. van der Knaap, Claire Wyman, Roland Kanaar, Paul Schedl e C. Peter Verrijzer. "Architecture of a Polycomb Nucleoprotein Complex". Molecular Cell 24, n. 1 (ottobre 2006): 91–100. http://dx.doi.org/10.1016/j.molcel.2006.08.007.

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6

Iwata, Shintaro, Hisanori Takenobu, Hajime Kageyama, Haruhiko Koseki, Takeshi Ishii, Atsuko Nakazawa, Shin-ichiro Tatezaki, Akira Nakagawara e Takehiko Kamijo. "Polycomb group molecule PHC3 regulates polycomb complex composition and prognosis of osteosarcoma". Cancer Science 101, n. 7 (7 aprile 2010): 1646–52. http://dx.doi.org/10.1111/j.1349-7006.2010.01586.x.

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7

Ali, Janann Y., e Welcome Bender. "Cross-Regulation among the Polycomb Group Genes in Drosophila melanogaster". Molecular and Cellular Biology 24, n. 17 (1 settembre 2004): 7737–47. http://dx.doi.org/10.1128/mcb.24.17.7737-7747.2004.

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Abstract (sommario):
ABSTRACT Genes of the Polycomb group in Drosophila melanogaster function as long-term transcriptional repressors. A few members of the group encode proteins found in two evolutionarily conserved chromatin complexes, Polycomb repressive complex 1 (PRC1) and the ESC-E(Z) complex. The majority of the group, lacking clear biochemical functions, might be indirect regulators. The transcript levels of seven Polycomb group genes were assayed in embryos mutant for various other genes in the family. Three Polycomb group genes were identified as upstream positive regulators of the core components of PRC1. There is also negative feedback regulation of some PRC1 core components by other PRC1 genes. Finally, there is positive regulation of PRC1 components by the ESC-E(Z) complex. These multiple pathways of cross-regulation help to explain the large size of the Polycomb group family of genes, but they complicate the genetic analysis of any single member.
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8

Iragavarapu, Akhil Gargey, Liqi Yao e Vignesh Kasinath. "Structural insights into the interactions of Polycomb Repressive Complex 2 with chromatin". Biochemical Society Transactions 49, n. 6 (8 novembre 2021): 2639–53. http://dx.doi.org/10.1042/bst20210450.

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Abstract (sommario):
Polycomb repressive complexes are a family of chromatin modifier enzymes which are critical for regulating gene expression and maintaining cell-type identity. The reversible chemical modifications of histone H3 and H2A by the Polycomb proteins are central to its ability to function as a gene silencer. PRC2 is both a reader and writer of the tri-methylation of histone H3 lysine 27 (H3K27me3) which serves as a marker for transcription repression, and heterochromatin boundaries. Over the last few years, several studies have provided key insights into the mechanisms regulating the recruitment and activation of PRC2 at Polycomb target genes. In this review, we highlight the recent structural studies which have elucidated the roles played by Polycomb cofactor proteins in mediating crosstalk between histone post-translational modifications and the recruitment of PRC2 and the stimulation of PRC2 methyltransferase activity.
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9

Lo, Stanley M., Nitin K. Ahuja e Nicole J. Francis. "Polycomb Group Protein Suppressor 2 of Zeste Is a Functional Homolog of Posterior Sex Combs". Molecular and Cellular Biology 29, n. 2 (3 novembre 2008): 515–25. http://dx.doi.org/10.1128/mcb.01044-08.

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Abstract (sommario):
ABSTRACT The Drosophila melanogaster Polycomb group protein Posterior Sex Combs is a component of Polycomb repressive complex 1 and is central to Polycomb group-mediated silencing. A related Polycomb group gene, Suppressor 2 of zeste, is thought to be partially redundant in function. The two proteins share a small region of homology but also contain regions of unconserved sequences. Here we report a biochemical characterization of Suppressor 2 of zeste. Like Posterior Sex Combs, Suppressor 2 of zeste binds DNA, compacts chromatin, and inhibits chromatin remodeling. Interestingly, the regions of the two proteins responsible for these activities lack sequence homology. Suppressor 2 of zeste can also replace Posterior Sex Combs in a functional complex with other Polycomb group proteins, but unlike with their biochemical activities, complex formation is mediated by the region of Suppressor 2 of zeste that is homologous to that of Posterior Sex Combs. Our results establish Suppressor 2 of zeste as a functional homolog of Posterior Sex Combs and suggest that the two proteins operate via similar molecular mechanisms.
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10

LaJeunesse, D., e A. Shearn. "E(z): a polycomb group gene or a trithorax group gene?" Development 122, n. 7 (1 luglio 1996): 2189–97. http://dx.doi.org/10.1242/dev.122.7.2189.

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Abstract (sommario):
The products of the Polycomb group of genes are cooperatively involved in repressing expression of homeotic selector genes outside of their appropriate anterior/posterior boundaries. Loss of maternal and/or zygotic function of Polycomb group genes results in the ectopic expression of both Antennapedia Complex and Bithorax Complex genes. The products of the trithorax group of genes are cooperatively involved in maintaining active expression of homeotic selector genes within their appropriate anterior/posterior boundaries. Loss of maternal and/or zygotic function of trithorax group genes results in reduced expression of both Antennapedia Complex and Bithorax Complex genes. Although Enhancer of zeste has been classified as a member of the Polycomb group, in this paper we show that Enhancer of zeste can also be classified as a member of the trithorax group. The requirement for Enhancer of zeste activity as either a trithorax group or Polycomb group gene depends on the homeotic selector gene locus as well as on spatial and temporal cues.
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Più fonti

Tesi sul tema "Polycomb complex"

1

Preissner, Tanja Stephanie. "The Polycomb-repressive complex 2 in X-inactivation". Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445872.

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2

Courel, María F. (María Federica). "The function of E2F6 in the Polycomb complex". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/86281.

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Abstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2005.
Cataloged from PDF version of thesis.
Includes bibliographical references.
The E2F family of transcription factors are known cell cycle regulators that function at the G1/S transition. Unlike other E2Fs, E2F6 does not activate transcription and is not regulated by pocket protein binding. Instead, this protein appears to repress transcription through the recruitment of the Polycomb Group (PcG) complex. This complex is responsible for the maintenance of Hox gene expression patterns during development and thus ensures the correct anterior-posterior segmentation of the embryo. Genetic ablation of PcG proteins leads to posterior transformations of the axial skeleton as well as other developmental abnormalities such as hematopoietic, cerebellar and smooth muscle defects. The PcG complex has been implicated in cell cycle control since several of its members, including the oncoprotein Bmi 1, appear to repress the transcription of p1 6INK4A and pI 9 ARF. In order to determine the biological function of E2F6, we have generated and characterized E2f6'- mice and mouse embryonic fibroblasts (MEFs). The mutant mice are viable and survive into adulthood with similar lifespan as their littermate controls. Furthermore, the E2f6 null MEFs are indistinguishable from wild-type MEFs in asynchronous proliferation, cell cycle re-entry from quiescence, senescence and E2F target genes expression levels. These findings suggest that E2F6 does not play a major role in cell cycle control or that its function can be compensated by the action of other factors. In fact, preliminary results from combined loss of E2f6 and Bmil suggest that E2F6 may take part in the Bmi 1-mediated control of the cell cycle. Furthermore, we found that the loss of E2F6 results in posterior axial skeleton transformations that are reminiscent of the Bmil-deficient mice defects. The study of the E2f6;Bmil compound mutant mice revealed a dosage-dependent synergism between E2F6 and Bmi 1. These results indicate that E2F6 participates in segmentation during murine development. As a whole, our work has provided proof that E2F6 is a bonafide Polycomb Group protein and, at the same time, has opened the field to a number of interesting questions.
by María F. Courel.
Ph. D.
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3

Grijzenhout, Anne Elizabeth. "Characterisation of AEBP2 : a polycomb repressive complex 2 component". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:159716a1-a03c-44f3-9fd1-0e88328caef6.

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4

Palau, de Miguel Anna. "Polycomb Repressive Complex 1 functions in differentiation and myelodysplastic syndromes". Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400293.

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Abstract (sommario):
Polycomb proteins are important epigenetic regulators involved in the maintenance of stemness and differentiation. In this thesis, I focused on the role of some Polycomb Repressive Complex 1 (PRC1) components. On the one hand, I studied the role of Cbx8 PRC1 component protein in the differentiation of mouse embryonic stem cells (mESCs). On the other hand, I analyzed the role of PRC1 components in a hematological disease-­related context which implies a defect in differentiation, the myelodysplastic syndrome (MDS). Specifically, I focused on RING1A PRC1-­component function in this disease. Our previous data showed that upon addition of retinoic acid (RA) during 3 days to E14 mouse ESC cell line, by which cells were prompted into the neuronal lineage, Cbx8 was upregulated both at mRNA and protein level. We performed a genome-­wide chromatin immunoprecipitation of endogenous Cbx8 coupled to direct massive parallel sequencing (ChIP-­seq) to assess the binding sites of Cbx8 genome-­ wide using IgG and Cbx8 ChIP in untreated mESC as negative controls. Our analysis identified 171 high confidence peaks. To our surprise, by crossing our data with previously published microarray analysis, we showed that several differentiation genes transiently recruit Cbx8 during their early activation. Depletion of Cbx8 by 2 different shRNA partially impaired the transcriptional activation of these genes as well as diminish Cbx8 recruitment to its target genes. Both interaction analysis, as well as chromatin immunoprecipitation experiments supported the idea that activating Cbx8 acts in the context of an intact PRC1 complex. Prolonged gene activation resulted in eviction of PRC1 despite persisting H3K27me3 and H2A ubiquitination. The composition of PRC1 is highly modular and changes when embryonic stem cells commit to differentiation. We further demonstrated that the exchange of Cbx7 for Cbx8 is required for the effective activation of differentiation genes. Taken together, our results establish a function for a Cbx8-­containing complex in facilitating the transition from a Polycomb-­ repressed chromatin state to an active state. In order to characterize the function of PRC1 in the pathogenesis of MDS we used publicly available expression datasets of PRC1 components from MDS patients and during normal myeloid differentiation to identify and quantify the level of relevant PRC1 complexes. From this data mining we selected four PRC1 components (CBX6, BMI1, RING1A and CBX7) and two PRC2 components (EZH2 and ASXL1) for further analysis. To study these PRC components we wished to use cell lines that are MDS-­related. For this reason, we extensively characterized 5 MDS/AML derived cell lines by conventional cytogenetics, single nucleotide polymorphism arrays, mutational panel of 83 MDS/AML relevant genes and immunoprofile. After this study, we selected SKK-­1 cell line as the most suitable model to study the function of the selected PRC1 components. Based on the finding that RING1A is highly expressed in hematopoietic stem cells and further overexpressed in patients with high risk MDS, we have analyzed the role of RING1A in cells. We found that RING1A inhibits differentiation in MDS-­derived AML cells and in primary human hematopoietic stem cells (HSCs). We further provide first evidence that pharmacological inhibition of RING1A could be therapeutic strategy by showing that the treatment of HSCs favors differentiation.
Les proteïnes Polycomb són importants reguladors epigenètics implicats en el manteniment de la pluripotència i la diferenciació. En aquesta tesi, m'he centrat en el paper d'alguns components del Polycomb Repressive Complex 1 (PRC1). D'una banda, he estudiat el paper de la proteïna Cbx8, component del PRC1, en la diferenciació de les cèl·lules mare embrionàries de ratolí (mESCs). D'altra banda, he analitzat el paper dels components del PRC1 en un una malaltia hematològica que implica un defecte en la diferenciació, la síndrome mielodisplàstica (SMD). En concret, m'he centrat en la funció de RING1A, component del PRC1, en aquesta malaltia. Les nostres dades anteriors van mostrar que després de l'addició d'àcid retinoic (RA) durant 3 dies a la línia cel·lular de mESCs Cbx8 es sobreexpressava, tant a nivell d'ARNm com de proteïnes. Vam realitzar una immunoprecipitació de cromatina del Cbx8 endogen a nivell de tot el genoma seguit de seqüenciació massiva (ChIP-­seq) per avaluar els punts d'unió de Cbx8 en tot el genoma utilitzant els ChIPs IgG i Cbx8 de mESC sense tractar com a controls negatius. La nostra anàlisi va identificar 171 pics d'alta confiança. Sorprenentment, en creuar les nostres dades amb l'anàlisi de microarrays publicat prèviament, es va demostrar que diversos gens de diferenciació transitòriament recluten Cbx8 durant la seva activació primerenca. El knockdown de Cbx8 per 2 shRNA diferents va afectar parcialment l'activació transcripcional d'aquests gens, així com va disminuir el reclutament de Cbx8 als seus gens diana. Tant l’anàlisi d'interacció per espectrometria de masses com els experiments de immunoprecipitació de la cromatina van donar suport a la idea que l'activació de Cbx8 actua en el context d'un complex PRC1 intacte. L’activació gènica prolongada va resultar en l’expulsió de PRC1 amb un H3K27me3 i H2AK119ub persistents. La composició del PRC1 és altament modular i canvia quan les cèl·lules mare embrionàries es diferencien. A més, vam demostrar que es requereix l'intercanvi de Cbx7 per Cbx8 per a l'activació efectiva dels gens de diferenciació. En conjunt, els nostres resultats estableixen una funció per a un complex que conté Cbx8 a l'hora de facilitar la transició d'un estat de cromatina reprimida per Polycomb a un estat actiu. Per tal de caracteritzar la funció de PRC1 en la patogènesi de SMD vam utilitzar dades d’expressió públicament disponibles de pacients amb SMD i durant la diferenciació mieloide normal per tal d’identificar i quantificar el nivell dels components de PRC1. A partir d'aquesta anàlisi es van seleccionar quatre components del PRC1 ( CBX6, BMI1, RING1A i CBX7) i dos components del PRC2 (EZH2 i ASXL1) per al seu posterior estudi. Vam decidir treballar amb línies cel·lulars relacionades amb MDS per tal d’estudiar aquests components PRC. Per aquesta raó, hem caracteritzat àmpliament 5 línies cel·lulars de leucèmia mieloide aguda (LMA) derivades de síndromes mielodisplàstiques (SMD) per citogenètica convencional, single nucleotide polymorphism arrays, un panell mutacional de 83 gens relacionats amb SMD /LMA i immunofenotip. Després d'aquest estudi, vam seleccionar la línia cel·lular SKK-­1 com el model més adequat per estudiar la funció dels components PRC1 seleccionats. Basant-­ nos en la troballa que RING1A està altament expressat en cèl·lules mare hematopoètiques i a més es sobreexpressa en pacients de SMD amb alt risc, hem analitzat la funció de RING1A. Vam trobar que RING1A inhibeix la diferenciació de la línia cel·lular de SMD/LMA i en cèl·lules mare hematopoètiques primàries. Proporcionem a més la primera evidència que la inhibició farmacològica de RING1A podria ser una estratègia terapèutica ja que el tractament en cèl·lules mare hematopoètiques afavoreix la diferenciació.
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5

Cedrone, L. "THE ROLE OF ENHANCED POLYCOMB REPRESSIVE COMPLEX 2 ACTIVITY IN TUMORIGENESIS". Doctoral thesis, Università degli Studi di Milano, 2017. http://hdl.handle.net/2434/468289.

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Abstract (sommario):
Polycomb Group of proteins are essential factors present in cells’ nuclei. These multiprotein complexes are key repressive chromatin factors that regulate cellular differentiation during development, contributing to the correct establishment of lineage-specific transcriptional programs. Moreover, they represent key factors of proliferation and deregulation of their levels and activity have been linked to the onset and development of several human cancers. Recently, gain of function heterozygous EZH2 mutations have been discovered in non-Hodgkin lymphomas and melanomas. These mutations cause an aminoacidic substitution within the EZH2 catalytic SET domain (Y641), resulting in increased H3K27me3 deposition. Very little is known about this mutated enzyme, therefore the aim of my thesis is trying to unravel the tumorigenic mechanisms underlying these mutations. To understand a general oncogenic role for this mutated enzyme, we used MEF as an alternative, simpler model system. We observed increased deposition of H3K27me3 without any relevant transcriptional alteration at steady state, confirming our results also in lymphoma cell lines. To investigate a cooperative transcriptional deregulation for mutant EZH2, we then subjected MEFs to three different stimuli (starvation, myc upregulation and reprogramming to pluripotency). Since we found this to be true only during cell-fate transition, we proposed a model in which the levels of the H3K27me3 are increasingly deposited where the mark is already present at steady state. This could be relevant in lymphomas, impeding centroblasts differentiation and resulting in tumorigenesis in the presence of concomitant oncogenic mutations. This observation could shed light on the molecular mechanisms underlying lymphomagenesis in patients.
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6

Ragazzini, Roberta. "Identification of a tissue-specific cofactor of polycomb repressive complex 2". Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066196/document.

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Abstract (sommario):
Répression des genes par le dépôt de la marque H3K27me3. Divers cofacteurs contrôlent sa fonction dans des cellules de différentes origines, comme les gametes. Au cours de ma thèse, j'ai utilisé des modèles murins ou un tag a été introduit dans les gènes Ezh2 et Ezh1, j'ai isolé des extraits nucléaires de testicules adultes entiers et identifié un nouveau polypeptide interagissant avec PRC2. Ce dernier est spécifiquement exprimé dans les gonades et sa fonction est inconnue. J'ai confirmé son interaction avec PRC2 et montré qu'il pourrait recruter PRC2 à la chromatine. Grâce à un modèle de souris knock-out, j'ai démontré que la protéine est nécessaire pour la fertilité féminine, alors que son ablation apporte une augmentation globale de la marque associée à PRC2, dans les cellules germinales masculines avec peu de conséquences sur la fertilité. J'ai également contribué à la caractérisation de l'interaction entre le long ARN non-codant HOTAIR et PRC2. Nombreux ARNnc ont été proposés pour moduler l'action des complexes modifiant la chromatine. Avec l'aide d'un nouveau système de recrutement artificiel d'ARN, l'expression induite par HOTAIR provoque une répression transgénique indépendamment de PRC2. La surexpression forcée de HOTAIR a également peu d'impact sur le transcriptome dans des cellules cancéreuses. En conclusion, la liaison PRC2 à l'ARN n'est pas requise pour le ciblage de la chromatine
The Polycomb Repressive Complex 2 (PRC2) plays an essential role in development by maintaining gene repression through the deposition of H3K27me3. A variety of cofactors have been shown to control its function in cells of various origins however little is known about PRC2 regulation during gametogenesis. During my PhD, I took advantage of murine models where Ezh2 and Ezh1 were knocked-in, I isolated nuclear extracts from whole adult testis and, identified a new polypeptide interacting with PRC2. This protein is specifically expressed in gonads, is of unknown function and does not contain any conserved domain. I have confirmed its interaction with PRC2, identified the domain of interaction with PRC2 and shown that it could tether PRC2 to chromatin. Thanks to a knockout mouse model, I demonstrated that the protein is required for female fertility, whereas its ablation brings to a global increase of H3K27me3 PRC2-associated mark in male germ cells with little consequences on male fertility. I also contributed to the characterization of the interplay between the long non-coding RNA (lncRNA) HOTAIR and PRC2 complex. Many lncRNAs have been proposed to modulate chromatin-modifying complexes action on chromatin. With the help of novel RNA-tethering system, HOTAIR inducible expression causes transgene repression independently from PRC2. Forced overexpression of HOTAIR also has little impact on transcriptome in breast cancer cells. Generally, PRC2 binding to RNA is not required for chromatin targeting. Taken together these results shed light to the mechanism of a new-identified cofactor regulating PRC2 in the gonads and contribute to dissect PRC2-RNA relationship at molecular level
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7

Ragazzini, Roberta. "Identification of a tissue-specific cofactor of polycomb repressive complex 2". Electronic Thesis or Diss., Paris 6, 2017. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2017PA066196.pdf.

Testo completo
Abstract (sommario):
Répression des genes par le dépôt de la marque H3K27me3. Divers cofacteurs contrôlent sa fonction dans des cellules de différentes origines, comme les gametes. Au cours de ma thèse, j'ai utilisé des modèles murins ou un tag a été introduit dans les gènes Ezh2 et Ezh1, j'ai isolé des extraits nucléaires de testicules adultes entiers et identifié un nouveau polypeptide interagissant avec PRC2. Ce dernier est spécifiquement exprimé dans les gonades et sa fonction est inconnue. J'ai confirmé son interaction avec PRC2 et montré qu'il pourrait recruter PRC2 à la chromatine. Grâce à un modèle de souris knock-out, j'ai démontré que la protéine est nécessaire pour la fertilité féminine, alors que son ablation apporte une augmentation globale de la marque associée à PRC2, dans les cellules germinales masculines avec peu de conséquences sur la fertilité. J'ai également contribué à la caractérisation de l'interaction entre le long ARN non-codant HOTAIR et PRC2. Nombreux ARNnc ont été proposés pour moduler l'action des complexes modifiant la chromatine. Avec l'aide d'un nouveau système de recrutement artificiel d'ARN, l'expression induite par HOTAIR provoque une répression transgénique indépendamment de PRC2. La surexpression forcée de HOTAIR a également peu d'impact sur le transcriptome dans des cellules cancéreuses. En conclusion, la liaison PRC2 à l'ARN n'est pas requise pour le ciblage de la chromatine
The Polycomb Repressive Complex 2 (PRC2) plays an essential role in development by maintaining gene repression through the deposition of H3K27me3. A variety of cofactors have been shown to control its function in cells of various origins however little is known about PRC2 regulation during gametogenesis. During my PhD, I took advantage of murine models where Ezh2 and Ezh1 were knocked-in, I isolated nuclear extracts from whole adult testis and, identified a new polypeptide interacting with PRC2. This protein is specifically expressed in gonads, is of unknown function and does not contain any conserved domain. I have confirmed its interaction with PRC2, identified the domain of interaction with PRC2 and shown that it could tether PRC2 to chromatin. Thanks to a knockout mouse model, I demonstrated that the protein is required for female fertility, whereas its ablation brings to a global increase of H3K27me3 PRC2-associated mark in male germ cells with little consequences on male fertility. I also contributed to the characterization of the interplay between the long non-coding RNA (lncRNA) HOTAIR and PRC2 complex. Many lncRNAs have been proposed to modulate chromatin-modifying complexes action on chromatin. With the help of novel RNA-tethering system, HOTAIR inducible expression causes transgene repression independently from PRC2. Forced overexpression of HOTAIR also has little impact on transcriptome in breast cancer cells. Generally, PRC2 binding to RNA is not required for chromatin targeting. Taken together these results shed light to the mechanism of a new-identified cofactor regulating PRC2 in the gonads and contribute to dissect PRC2-RNA relationship at molecular level
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Sanulli, Serena. "Polycomb repressive complex 2 and jarid2 in the establishment of repressive chromatin state". Paris 6, 2013. http://www.theses.fr/2013PA066429.

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RC2 contribue au maintien de la répression transcriptionnelle au cours du développement par la di- et tri- méthylation de H3K27. PRC2 est nécessaire à de nombreux processus biologiques tels que le renouvellement et différenciation des cellules souches et le maintien de l’identité cellulaire. Malgré de nombreuses recherches, les mécanismes qui régulent la dynamique du recrutement de PRC2 à la chromatine sont peu compris. Des études récentes ont montré que Jarid2 est un cofacteur de PRC2 qui régulerait son ciblage à la chromatine. Pendant ma thèse, je me suis concentrée sur l’étude des mécanismes moléculaires de régulation du recrutement de PRC2 dépendents de Jarid2. J’ai montré que Jarid2 est méthylé par PRC2 et que cette méthylation stimule l’activité enzymatique de PRC2. Des expériences in vitro et in vivo ont permis de montrer que la méthylation de Jarid2 est impliquée dans la relocalisation de PRC2 à de nouvelles régions du génome, initialisant l’activité enzymatique de PRC2. J’ai également contribué à la caractérisation d’une nouvelle protéine contenant un domaine SET codée par la bactérie L. Pneumophila. Cette protéine, qui est secrétée par la bactérie lors de l’infection, modifie la chromatine des cellules hôtes en méthylant H3K14, une modification normalement absente de la chromatine des cellules hôtes. En empêchant l’acétylation de H3K14, cette modification induirait une répression transcriptionnelle globale afin de limiter les défenses de la cellule hôte. Ces découvertes ouvrent de nouvelles perspectives sur les mécanismes de régulation et la fonction des enzymes méthyltransférases lors du développement et aussi en réponse aux infections cellulaires
Polycomb Repressive complex 2 (PRC2) contributes to the maintenance of epigenetic silencing established during development through the di- and trimethylation of H3K27. PRC2 complex is crucial for several biological processes, including stem cell self-renewal and differentiation, and maintenance of cell identity. Despite intensive research, the mechanisms that dynamically regulate PRC2 recruitment to the chromatin are still poorly understood. Recent studies identified Jarid2 as a cofactor of PRC2 and proposed this protein as a regulator of PRC2 targeting. During my PhD, I focused on the molecular mechanisms responsible for PRC2 chromatin targeting mediated by Jarid2 cofactor. I demonstrated that Jarid2 is methylated by PRC2 and that its methylation stimulates PRC2 enzymatic activity. Biochemical and in vivo approaches revealed that Jarid2 methylation acts during the de novo targeting of PRC2 complex to prime PRC2 activity and ensure the establishment of H3K27me3 at new genomic sites. I also contributed to the characterization of a novel SET-domain containing protein encoded by the bacteria L. Pneumophila. This protein, secreted by the bacteria after cellular infection, is targeted to the host chromatin to induce a unique modification, H3K14me. This mark, normally not present in mammalian host cells, prevents H3K14 acetylation and causes global transcriptional repression to circumvent cellular defense. These findings provided new perspectives about the regulation and function of histone-methyltransferase proteins during development and cell fate decision, as well as during cellular infections
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Asamaowei, Inemo E. "The Role of Polycomb Repressive Complex 2 in Epidermal Homeostasis and Hair Growth". Thesis, University of Bradford, 2017. http://hdl.handle.net/10454/16844.

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Abstract (sommario):
Polycomb repressive complex 2 (PRC2) catalyses the methylation of ‘Lys-27’ of histone H3, leading to transcriptional repression of target genes through its catalytic subunit Enhancer of zeste homolog 1/2 (EZH1/2). PRC2 functions as a critical regulator of stem cells in mouse embryonic and adult tissues. However, the role of PRC2 in human skin remains largely unknown. This study investigated the role of PRC2 in human epidermal homeostasis and hair growth. The expression of EZH2 was elevated in differentiating suprabasal layers of the human epidermis. Consistently, EZH1/2 expression and enzymatic activity was upregulated in differentiating primary human keratinocytes (NHEKs) in vitro. Inhibition of EZH2 and Embryonic ectoderm development (EED) in NHEKs stimulated the expression of differentiation-associated genes, therefore leading to their premature differentiation; while inhibition of EZH1/2 reduced cell proliferation and promoted apoptosis. Silencing of EZH2 in NHEKs induced complex changes in gene expression programmes, including the upregulation of terminal differentiation genes, such as Filaggrin. EZH2 expression was downregulated in aged keratinocytes accompanied with upregulation of senescence-associated genes, p16INK4A and p19INK4D, suggesting EZH2 involvement in epidermal aging. In human anagen hair follicle (HF), EZH2 was detected in stem and progenitor cells; and hair matrix keratinocytes. Silencing EZH2 in HFs accelerated anagen-catagen transition and retarded hair growth accompanied by decreased proliferation and increased apoptosis. Silencing EZH2 in outer root sheath keratinocytes resulted in upregulation of p14ARF and K15, suggesting EZH2 involvement in regulating proliferation and stem cell activity. Thus, this study demonstrates that PRC2-mediated repression is crucial for epidermal homeostasis and hair growth. Modulating the activities of PRC2 in skin might offer a new therapeutic approach for disorders of epidermal differentiation and hair growth.
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Sharif, Azar. "Structural characterization of the polycomb repressor complex 1 binding partner ubiquitin specific protease 11". Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/39355.

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Abstract (sommario):
Ubiquitin Specific Protease 11 (USP11), USP4 and USP15 are highly conserved and are characterised by an N-terminal 'domain present in ubiquitin specific proteases' (DUSP) and 'ubiquitin-like' (UBL) domains. This DUSP-UBL (DU) domain is thought to be involved in substrate recognition. It was shown that USP11 co-purifies with human Polycomb Repressive Complex type 1 (PRC1) and regulates the stability of the E3 ligase component of PRC1 (Maertens et al, 2010). PRC1 repress transcription from the INK4a tumour suppressor locus. Hence knockdown of USP11 in primary human fibroblasts causes de-repression of INK4a, followed by a senescence-like proliferative arrest. In this project we aimed to map the interaction between USP11 and PRC1 components (BMI1, RING2, MEL18 and CBX8). We used two methods to investigate their interactions; yeast two-hybrid and in vitro pull down. Unexpectedly, we could not confirm a direct interaction between USP11 and any PRC1 component. We hypothesize that the lack of post-translation modifications, the presence of fusion tags and/or the need of a multi-subunit PRC1 complex might be needed to observe a high affinity interaction. We also aimed to map the interaction between three PRC1 components; RING2, BMI1 and RYBP, with the ultimate aim of solving the X-ray structure of the complex. The main obstacle in this project was to express, extract and purify these proteins at high levels in bacterial culture. Preliminary data suggests that RYBP and BMI1 do not interact directly. Here we report the 3.6 Å resolution X-ray structure of the human USP11 DU. The sequence linking the DUSP and UBL domains, the DU finger, could not be assigned in the electron density map due to low resolution. Comparison with the related USP4 DU crystal structure reveals that the structures are mostly conserved.
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Capitoli di libri sul tema "Polycomb complex"

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Guo, Yiran, Yao Yu e Gang Greg Wang. "Polycomb Repressive Complex 2 in Oncology". In Cancer Treatment and Research, 273–320. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-45654-1_9.

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Liu, Xin. "A Structural Perspective on Gene Repression by Polycomb Repressive Complex 2". In Subcellular Biochemistry, 519–62. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-58971-4_17.

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Shirai, Manabu, Yoshihiro Takihara e Takayuki Morisaki. "Pcgf5 Contributes to PRC1 (Polycomb Repressive Complex 1) in Developing Cardiac Cells". In Etiology and Morphogenesis of Congenital Heart Disease, 305–12. Tokyo: Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-54628-3_43.

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Brahmachari, Vani, e Shruti Jain. "Polycomb Complexes". In Encyclopedia of Systems Biology, 1720. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4419-9863-7_854.

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Luo, Ming, Mingzhu Luo, Fred Berger, E. S. Dennis, Jim W. Peacock e Abed Chaudhury. "DNA-METHYLTRANSFERASE 1 is a Member of FIS Polycomb Complex and is Involved in Seed Development in Arabidopsis". In Biotechnology and Sustainable Agriculture 2006 and Beyond, 131–33. Dordrecht: Springer Netherlands, 2007. http://dx.doi.org/10.1007/978-1-4020-6635-1_16.

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Palacios, Daniela. "The Dynamics of Polycomb Complexes". In Methods in Molecular Biology, 139–42. New York, NY: Springer New York, 2016. http://dx.doi.org/10.1007/978-1-4939-6380-5_12.

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Duarte-Aké, Fátima, Geovanny Nic-Can e Clelia De-la-Peña. "Somatic Embryogenesis: Polycomb Complexes Control Cell-to-Embryo Transition". In Epigenetics in Plants of Agronomic Importance: Fundamentals and Applications, 339–54. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-14760-0_13.

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Vidal, Miguel. "Polycomb Complexes: Chromatin Regulators Required for Cell Diversity and Tissue Homeostasis". In Transcriptional and Epigenetic Mechanisms Regulating Normal and Aberrant Blood Cell Development, 95–139. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-45198-0_5.

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Paro, Renato, Ueli Grossniklaus, Raffaella Santoro e Anton Wutz. "Cellular Memory". In Introduction to Epigenetics, 49–66. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-68670-3_3.

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AbstractThe identity of cells in an organism is largely defined by their specific transcriptional profile. During cell division, these profiles need to be faithfully inherited to the daughter cells to ensure the maintenance of cell structure and function in a cell lineage. Here, you will learn how two groups of chromatin regulators, the Polycomb group (PcG) and the Trithorax group (TrxG), act in an antagonistic manner to maintain differential gene expression states. Members of the PcG cooperate in large multiprotein complexes to modify histones with repressive marks, resulting in condensed chromatin domains. Conversely, the TrxG proteins counteract the repressed domains by opening nucleosomal structures and establishing activating histone modifications. PcG and TrxG proteins are evolutionary highly conserved and control diverse processes, such as the identity of stem cells in mammalian development to the process of vernalization in plants.
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Holoch, D., e R. Margueron. "Polycomb Repressive Complex 2 Structure and Function". In Polycomb Group Proteins, 191–224. Elsevier, 2017. http://dx.doi.org/10.1016/b978-0-12-809737-3.00009-x.

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Atti di convegni sul tema "Polycomb complex"

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Iwata, Shintaro. "Abstract 4898: Polycomb group molecule PHC3 regulates polycomb complex composition and prognosis of osteosarcoma". In Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC. American Association for Cancer Research, 2010. http://dx.doi.org/10.1158/1538-7445.am10-4898.

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Cao, Qi, Ram Mani, Bushra Ateeq, Saravana M. Dhanasekaren, Irfan Asangani, Jindan Yu, John Prensner et al. "Abstract 2795: An onco-protein axis linking polycomb repressive complex 2 and polycomb repressive complex 1 through miRNAs in cancer". In Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL. American Association for Cancer Research, 2011. http://dx.doi.org/10.1158/1538-7445.am2011-2795.

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ZHU, Junyu, Lili Li, Connie W. Hui, Joanna H. Tong, Raymond Chan, Chi Hang Wong, Qiyong Ai et al. "Abstract 2923: Targeting the polycomb repressive complex-2 related proteins in nasopharyngeal carcinoma". In Proceedings: AACR Annual Meeting 2020; April 27-28, 2020 and June 22-24, 2020; Philadelphia, PA. American Association for Cancer Research, 2020. http://dx.doi.org/10.1158/1538-7445.am2020-2923.

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Chen, Fan, e Christine F. Brainson. "Abstract 5189: Activity of polycomb repressive complex 2 determines sensitivity to epigenetic therapy". In Proceedings: AACR Annual Meeting 2019; March 29-April 3, 2019; Atlanta, GA. American Association for Cancer Research, 2019. http://dx.doi.org/10.1158/1538-7445.sabcs18-5189.

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Chen, Fan, e Christine F. Brainson. "Abstract 5189: Activity of polycomb repressive complex 2 determines sensitivity to epigenetic therapy". In Proceedings: AACR Annual Meeting 2019; March 29-April 3, 2019; Atlanta, GA. American Association for Cancer Research, 2019. http://dx.doi.org/10.1158/1538-7445.am2019-5189.

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Bakhtiari, Mojtaba, Aria L. Byrd, Fan Chen, Alexsandr Lukyanchuk, Tanner J. DuCote e Christine Fillmore Brainson. "Abstract PR03: Metabolic control of Polycomb Repressive Complex 2 in Lung Disease and Lung Cancer". In Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020. American Association for Cancer Research, 2020. http://dx.doi.org/10.1158/1538-7445.epimetab20-pr03.

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Bentrop, M., C. Vokuhl, D. von Schweinitz e R. Kappler. "Inhibition of the polycomb repressive complex 1 (PRC1) as a therapeutic option in childhood liver tumors". In 32. Jahrestagung der Kind-Philipp-Stiftung für pädiatrisch onkologische Forschung. Georg Thieme Verlag KG, 2019. http://dx.doi.org/10.1055/s-0039-1687161.

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Crosby, Lynn M., e Christopher Waters. "A Role For The Polycomb Repressor Complex 2 Protein EZH2 In Rat Alveolar Type II Cell Wound Healing". In American Thoracic Society 2011 International Conference, May 13-18, 2011 • Denver Colorado. American Thoracic Society, 2011. http://dx.doi.org/10.1164/ajrccm-conference.2011.183.1_meetingabstracts.a5108.

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Hamaidia, Malik, Clotilde Hoyos e Luc L. Willems. "Abstract 3800: Inhibition of Polycomb Repressive Complex 2 EZH2 lysine methyltransferase improves tumoricidal activity of macrophages towards mesothelioma cells". In Proceedings: AACR Annual Meeting 2018; April 14-18, 2018; Chicago, IL. American Association for Cancer Research, 2018. http://dx.doi.org/10.1158/1538-7445.am2018-3800.

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Qian, Tingting, Jeong-Yeon Lee, Hyun-Jun Kim e Gu Kong. "Abstract LB-96: Id1 enhances RING1b E3 ubiquitin ligase activity through the Mel-18/Bmi-1 polycomb group complex". In Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC. American Association for Cancer Research, 2010. http://dx.doi.org/10.1158/1538-7445.am10-lb-96.

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Rapporti di organizzazioni sul tema "Polycomb complex"

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Ohad, Nir, e Robert Fischer. Regulation of plant development by polycomb group proteins. United States Department of Agriculture, gennaio 2008. http://dx.doi.org/10.32747/2008.7695858.bard.

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Abstract (sommario):
Our genetic and molecular studies have indicated that FIE a WD-repeat Polycomb group (PcG) protein takes part in multi-component protein complexes. We have shown that FIE PcG protein represses inappropriate programs of development during the reproductive and vegetative phases of the Arabidopsis life cycle. Moreover, we have shown that FIE represses the expression of key regulatory genes that promote flowering (AG and LFY), embryogenesis (LEC1), and shoot formation (KNAT1). These results suggest that the FIE PcG protein participates in the formation of distinct PcG complexes that repress inappropriate gene expression at different stages of plant development. PcG complexes modulate chromatin compactness by modifying histones and thereby regulate gene expression and imprinting. The main goals of our original project were to elucidate the biological functions of PcG proteins, and to understand the molecular mechanisms used by FIE PcG complexes to repress the expression of its gene targets. Our results show that the PcG complex acts within the central cell of the female gametophyte to maintain silencing of MEA paternal allele. Further more we uncovered a novel example of self-imprinting mechanism by the PgG complex. Based on results obtained in the cures of our research program we extended our proposed goals and elucidated the role of DME in regulating plant gene imprinting. We discovered that in addition to MEA,DME also imprints two other genes, FWA and FIS2. Activation of FWA and FIS2 coincides with a reduction in 5-methylcytosine in their respective promoters. Since endosperm is a terminally differentiated tissue, the methylation status in the FWA and FIS2 promoters does not need to be reestablished in the following generation. We proposed a “One-Way Control” model to highlight differences between plant and animal genomic imprinting. Thus we conclude that DEMETER is a master regulator of plant gene imprinting. Future studies of DME function will elucidate its role in processes and disease where DNA methylation has a key regulatory role both in plants and animals. Such information will provide valuable insight into developing novel strategies to control and improve agricultural traits and overcome particular human diseases.
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Ohad, Nir, e Robert Fischer. Regulation of Fertilization-Independent Endosperm Development by Polycomb Proteins. United States Department of Agriculture, gennaio 2004. http://dx.doi.org/10.32747/2004.7695869.bard.

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Abstract (sommario):
Arabidopsis mutants that we have isolated, encode for fertilization-independent endosperm (fie), fertilization-independent seed2 (fis2) and medea (mea) genes, act in the female gametophyte and allow endosperm to develop without fertilization when mutated. We cloned the FIE and MEA genes and showed that they encode WD and SET domain polycomb (Pc G) proteins, respectively. Homologous proteins of FIE and MEA in other organisms are known to regulate gene transcription by modulating chromatin structure. Based on our results, we proposed a model whereby both FIE and MEA interact to suppress transcription of regulatory genes. These genes are transcribed only at proper developmental stages, as in the central cell of the female gametophyte after fertilization, thus activating endosperm development. To test our model, the following questions were addressed: What is the Composition and Function of the Polycomb Complex? Molecular, biochemical, genetic and genomic approaches were offered to identify members of the complex, analyze their interactions, and understand their function. What is the Temporal and Spatial Pattern of Polycomb Proteins Accumulation? The use of transgenic plants expressing tagged FIE and MEA polypeptides as well as specific antibodies were proposed to localize the endogenous polycomb complex. How is Polycomb Protein Activity Controlled? To understand the molecular mechanism controlling the accumulation of FIE protein, transgenic plants as well as molecular approaches were proposed to determine whether FIE is regulated at the translational or posttranslational levels. The objectives of our research program have been accomplished and the results obtained exceeded our expectation. Our results reveal that fie and mea mutations cause parent-of-origin effects on seed development by distinct mechanisms (Publication 1). Moreover our data show that FIE has additional functions besides controlling the development of the female gametophyte. Using transgenic lines in which FIE was not expressed or the protein level was reduced during different developmental stages enabled us for the first time to explore FIE function during sporophyte development (Publication 2 and 3). Our results are consistent with the hypothesis that FIE, a single copy gene in the Arabidopsis genome, represses multiple developmental pathways (i.e., endosperm, embryogenesis, shot formation and flowering). Furthermore, we identified FIE target genes, including key transcription factors known to promote flowering (AG and LFY) as well as shoot and leaf formation (KNAT1) (Publication 2 and 3), thus demonstrating that in plants, as in mammals and insects, PcG proteins control expression of homeobox genes. Using the Yeast two hybrid system and pull-down assays we demonstrated that FIE protein interact with MEA via the N-terminal region (Publication 1). Moreover, CURLY LEAF protein, an additional member of the SET domain family interacts with FIE as well. The overlapping expression patterns of FIE, with ether MEA or CLF and their common mutant phenotypes, demonstrate the versatility of FIE function. FIE association with different SET domain polycomb proteins, results in differential regulation of gene expression throughout the plant life cycle (Publication 3). In vitro interaction assays we have recently performed demonstrated that FIE interacts with the cell cycle regulatory component Retinobalsoma protein (pRb) (Publication 4). These results illuminate the potential mechanism by which FIE may restrain embryo sac central cell division, at least partly, through interaction with, and suppression of pRb-regulated genes. The results of this program generated new information about the initiation of reproductive development and expanded our understanding of how PcG proteins regulate developmental programs along the plant life cycle. The tools and information obtained in this program will lead to novel strategies which will allow to mange crop plants and to increase crop production.
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Ohad, Nir, e Robert Fischer. Control of Fertilization-Independent Development by the FIE1 Gene. United States Department of Agriculture, agosto 2000. http://dx.doi.org/10.32747/2000.7575290.bard.

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Abstract (sommario):
A fundamental problem in biology is to understand how fertilization initiates reproductive development. During plant reproduction, one sperm cell fuses with the egg to form an embryo, whereas a second sperm cell fuses with the adjacent central cell nucleus to form the endosperm tissue that supports embryo and/or seedling development. To understand the mechanisms that initiate reproduction, we have isolated mutants of Arabidopsis that allow for replication of the central cell and subsequent endosperm development without fertilization. In this project we have cloned the MEA gene and showed that it encode a SET- domain polycomb protein. Such proteins are known to form chromatin-protein complexes that repress homeotic gene transcription and influence cell proliferation from Drosophylla to mammals. We propose a model whereby MEA and an additional polycomb protein we have cloned, FIE , function to suppress a critical aspect of early plant reproduction and endosperm development, until fertilization occurs. Using a molecular approach we were able to determine that FIE and MEA interact physically, suggesting that these proteins have been conserved also during the evolution of flowering plants. The analysis of MEA expression pattern revealed that it is an imprinted gene that displays parent-of- origin-dependent monoallelic expression specifically in the endosperm tissue. Silencing of the paternal MEA allele in the endosperm and the phenotype of mutant mea seeds support the parental conflict theory for the evolution of imprinting in plants and mammals. These results contribute new information on the initiation of endosperm development and provide a unique entry point to study asexual reproduction and apomixis which is expected to improve crop production.
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Ori, Naomi, e Mark Estelle. Specific mediators of auxin activity during tomato leaf and fruit development. United States Department of Agriculture, gennaio 2012. http://dx.doi.org/10.32747/2012.7597921.bard.

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Abstract (sommario):
The plant hormone auxin is involved in numerous developmental processes, including leaf and fruit development. The tomato (Solanumlycopersicum) gene ENTIRE (E) encodes an auxin-response inhibitor from the Aux/IAA family. While most loss-offunction mutations in Aux/IAA genes are similar to the wild type due to genetic redundancy, entire (e) mutants show specific effects on leaf and fruit development. e mutants have simple leaves, in contrast to the compound leaves of wild type tomatoes. In addition, e plants produce parthenocarpic fruits, in which fruit set occurs independently of fertilization. The aim of this research program was to utilize the e mutation to identify and characterize genes that mediate the specific effect of auxin in leaf and fruit development. The specific objectives of the project were to: 1. Characterize and map modifiers of the e leaf phenotype. 2. Characterize and map suppressors of the e fruit phenotype. 3. Dissect the developmental specificity of the E gene. 4. Examine the effect of fruit-overexpression of identified genes on fruit set and seed production. To identify mediators of auxin in leaf development, we mainly focused on one mutant, crawling elephant (crel, previously called t282), which showed substantial suppression of the e phenotype and other auxin-relatedphenotypes. We have identified the CREL gene as a homolog of the Arabidopsis VRN5 gene, involved in recruiting polycomb silencing complexes to specific targets. We showed that CREL affects auxin sensitivity in tomato. Suppressors of the e fruit phenotype have been further characterized and selected for more profound effects. Expression profiling by RNAseq was used to analyze the effect of e as well as crel on gene expression in leaves and fruits. This analysis has identified putative E and CREL targets. We have initiated studies to assess the role of some of these targets in flower and fruit development. The research has identified potential mediators of auxin response in leaf, flower and fruit development.
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