Добірка наукової літератури з теми "19S regulatory particle"

Abstract Major histocompatibility class II molecules are cell surface glycoproteins that present extracellular peptides to CD4+ T cells and initiate adaptive immune responses. MHC II molecules are inducibly expressed in response to interferon gamma and are tightly regulated at the level of transcription by a master regulator, the class II transactivator, CIITA. We have recently shown that the 26S proteasome, itself a master regulator of proteins, regulates transcription initiation at interferon gamma inducible CIITApIV and MHC II genes in a degradation independent manner. The 26S proteasome consists of two major subunits, a 19S regulatory particle and a 20S proteolytic core. The 19S contains six ATPases which associate with MHC II and CIITA promoters and play important roles in transcription initiation by recruiting critical histone modifying enzymes. To determine if the 19S ATPases function in transcription elongation, 19S ATPase binding and activity in CIITApIV coding regions was analyzed. ChIP assays indicate significant binding of 19S ATPases in CIITA coding regions, and knockdown of 19S ATPases results in significant decreases in RNA pol II binding throughout CIITApIV coding regions. Further, knockdown of 19S ATPases has minimal impact on the expression of short CIITApIV transcripts but significant negative impact on long transcript expression, indicating roles for 19S ATPases in RNA pol II processivity at CIITApIV and likely other inducible mammalian genes.

The 26S proteasome is a macromolecular complex that degrades proteins maintaining cell homeostasis; thus, determining its structure is a priority to understand its function. Although the 20S proteasome’s structure has been known for some years, the highly dynamic nature of the 19S regulatory particle has presented a challenge to structural biologists. Advances in cryo-electron microscopy (cryo-EM) made it possible to determine the structure of the 19S regulatory particle and showed at least seven different conformational states of the proteasome. However, there are still many questions to be answered. Cross-linking mass spectrometry (CLMS) is now routinely used in integrative structural biology studies, and it promises to take integrative structural biology to the next level, answering some of these questions.

The 26S proteasome consists of the 20S proteasome (core particle) and the 19S regulatory particle made of the base and lid substructures, and it is mainly localized in the nucleus in yeast. To examine how and where this huge enzyme complex is assembled, we performed biochemical and microscopic characterization of proteasomes produced in two lid mutants, rpn5-1 and rpn7-3, and a base mutant ΔN rpn2, of the yeast Saccharomyces cerevisiae. We found that, although lid formation was abolished in rpn5-1 mutant cells at the restrictive temperature, an apparently intact base was produced and localized in the nucleus. In contrast, in ΔN rpn2 cells, a free lid was formed and localized in the nucleus even at the restrictive temperature. These results indicate that the modules of the 26S proteasome, namely, the core particle, base, and lid, can be formed and imported into the nucleus independently of each other. Based on these observations, we propose a model for the assembly process of the yeast 26S proteasome.

Ubiquitin-independent protein degradation via the 20S proteasome without the 19S regulatory particle has gained increasing attention over the last years. The degradation of the ubiquitin-like modifier FAT10 by the 20S proteasome was investigated in this study. We found that FAT10 was rapidly degraded by purified 20S proteasomes in vitro, which was attributed to the weak folding of FAT10 and the N-terminally disordered tail. To confirm our results in cellulo, we established an inducible RNA interference system in which the AAA-ATPase Rpt2 of the 19S regulatory particle is knocked down to impair the function of the 26S proteasome. Using this system, degradation of FAT10 in cellulo was strongly dependent on functional 26S proteasome. Our data indicate that in vitro degradation studies with purified proteins do not necessarily reflect biological degradation mechanisms occurring in cells and, therefore, cautious data interpretation is required when 20S proteasome function is studied in vitro.

The interaction of the 19S regulatory particle of the 26S proteasome with ubiquitylated proteins leads to gate opening of the 20S core particle and increases its proteolytic activity by binding of the ubiquitin chain to the inhibitory deubiquitylation enzyme USP14 on the 19S regulatory subunit RPN1. Covalent modification of proteins with the cytokine inducible ubiquitin-like modifier FAT10 is an alternative signal for proteasomal degradation. Here, we report that FAT10 and its interaction partner NUB1L facilitate the gate opening of the 20S proteasome in an ubiquitin- and USP14-independent manner. We also show that FAT10 is capable to activate all peptidolytic activities of the 26S proteasome, however only together with NUB1L, by binding to the UBA domains of NUB1L and thereby interfering with NUB1L dimerization. The binding of FAT10 to NUB1L leads to an increased affinity of NUB1L for the subunit RPN1. In conclusion, the herein described cooperation of FAT10 and NUB1L is a substrate-induced mechanism to activate the 26S proteasome.

Le paludisme, causé par le parasite Plasmodium est la parasitose la plus létale au monde, avec plus de 600 000 décès en 2021, et touche en grande majorité des enfants de moins de 5 ans principalement en Afrique. Contre cette maladie infectieuse, le vaccin RTS,S/A01 est recommandé depuis 2021 par l'OMS. Néanmoins, son efficacité relative, associée aux résistances apparues chez le parasite contre les combinaisons chimio-thérapeutiques à base d'artémisinine (Artemisinin Combined Therapies) et aux résistances du vecteur aux insecticides, engendrent la nécessité de poursuivre les efforts de recherche pour mieux comprendre la biologie du parasite et concevoir de nouvelles molécules anti-parasitaires. La phosphorylation réversible des protéines joue un rôle crucial lors du développement du parasite. Ainsi, il a récemment été démontré que la sérine/thréonine phosphatase PP1 était essentielle lors des stades tardifs de la schizogonie, notamment lors de la phase de sortie (« egress ») du globule rouge. Notre équipe étudie les régulateurs de la sous-unité catalytique de la phosphatase (PP1c). Au cours de deux études d'interactome de PP1c chez Plasmodium berghei, notre équipe a observé une interaction potentielle entre PP1c et différentes protéines du protéasome parasitaire, dont l'AAA-ATPase PbRpt3 (PBANKA_0715600). Cette protéine possède deux motifs RVxF, décrits pour être majoritairement présents chez les protéines interagissant avec PP1c. De plus, grâce à des approches globales, Rpt3 a été prédite comme essentielle chez P. falciparum, alors que chez P. berghei les parasites déficients pour cette ATPase présentent un phénotype lent. Le protéasome 26S est un complexe protéique impliqué dans la dégradation des protéines, contribuant à l'homéostasie et à la réponse au stress des cellules eucaryotes. Il est composé d'un complexe 20S portant l'activité catalytique, associé à un ou deux complexes régulateurs 19S composé de protéines ATPases (Rpt) et non-ATPases (Rpn). La protéine PbRpt3 appartiendrait au complexe 19S du protéasome parasitaire. Au cours de ma thèse, j'ai caractérisé la sous-unité régulatrice PbRpt3, démontré qu'elle interagissait avec PP1c in vitro, et qu'elle activait la fonction phosphatase de PP1c à la fois in vitro et dans un modèle hétérologue d'ovocytes de Xénope. Par une approche de mutagenèse dirigée, nous avons observé que les motifs RVxF de PbRpt3 étaient impliqués dans sa fonction de liaison et de régulation de PP1c. Nous avons construit un modèle 3D de la protéine PbRpt3 par homologie comparative, ce qui nous a permis de prédire les acides aminés intervenant dans la stabilisation de l'ATP. La mutation de ces acides aminés, combinée à l'approche en ovocytes de Xénope a conduit à montrer que l'activité enzymatique de PbRpt3 serait impliquée dans sa fonction d'activation de la phosphatase PP1c. Grâce à des études de génétique inverse, nous suggérons un rôle essentiel de Rpt3 lors des stades intra-érythrocytaires chez P. berghei car aucune lignée de parasites déficients pour PbRpt3 n'a été obtenue chez la souris malgré de nombreuses tentatives de clonage et l'utilisation du système PlasmoGem. Une approche de Knock-in, en utilisant le tag mCherry a permis de localiser la protéine au cours du cycle intra-érythrocytaire, avec une présence dans le cytoplasme lors des stades trophozoïte à schizonte, et une concentration localisée dans le noyau chez les gamétocytes. Enfin, des immunoprécipitations suivies d'une analyse en spectrométrie de masse ont permis de caractériser l'interactome de PbRpt3 chez le parasite au stade schizonte. Ainsi, nous avons confirmé que PbRpt3 appartiendrait au complexe protéasome 19S, et observé que cette ATPase s'associe à plusieurs protéines connues pour lier les phospholipides membranaires. Ces observations suggèrent que PbRpt3 pourrait jouer un rôle direct, ou via ses partenaires, dans la dynamique des membranes chez P. berghei
Malaria, caused by the Plasmodium parasite, is the most lethal parasitosis in the world, with more than 600,000 deaths in 2021, and mostly affects children under the age of 5, mainly in Africa. The RTS,S/A01 vaccine against this infectious disease has been recommended by the WHO since 2021. However, its relative efficacy, combined with the parasite's resistance to artemisinin-based chemo-therapeutic combinations (Artemisinin Combined Therapies) and the vector's resistance to insecticides, implies that further research is needed to gain a better understanding of the parasite's biology and design new anti-parasitic molecules. Reversible protein phosphorylation plays a crucial role in the development of the parasite. For example, it has recently been shown that the serine/threonine phosphatase PP1 is essential during the late stages of schizogony, particularly during the egress phase of the red blood cell. Our team studies the regulators of the catalytic subunit of the phosphatase (PP1c). Two PP1c interactome studies in Plasmodium berghei, have led our team to observe a potential interaction between PP1c and various proteins belonging to the parasite proteasome, including the AAA-ATPase PbRpt3 (PBANKA_0715600), which possesses two RVxF motifs, described as being predominantly present in proteins interacting with PP1c. Furthermore, using global approaches, Rpt3 was predicted to be essential in P. falciparum, whereas in P. berghei parasites deficient for this ATPase show a slow phenotype. The 26S proteasome is a protein complex involved in protein degradation, contributing to homeostasis and the stress response in eukaryotic cells. It is composed of a 20S complex carrying the catalytic activity, associated with one or two 19S regulatory complexes composed of ATPase (Rpt) and non-ATPase (Rpn) proteins. The PbRpt3 protein is thought to belong to the 19S complex of the parasite proteasome. During my thesis, I characterised the PbRpt3 regulatory subunit, demonstrated that it interacts with PP1c in vitro, and that it activates the phosphatase function of PP1c both in vitro and in a heterologous model of Xenopus oocytes. Using a site-directed mutagenesis approach, we observed that the RVxF motifs of PbRpt3 were involved in its binding to PP1c, and in the regulatory function towards this phosphatase. We built a 3D model of the PbRpt3 protein by comparative homology, which enabled us to predict the amino acids involved in ATP stabilisation. The mutation of these amino acids, combined with the Xenopus oocyte approach, led us to show that the enzymatic activity of PbRpt3 would be involved in the activation of the PP1c phosphatase. Using reverse genetics studies, we suggest an essential role for Rpt3 during the intra-erythrocytic stages in P. berghei, as no PbRpt3-deficient parasites were obtained in mice despite numerous cloning attempts and the use of the PlasmoGem system. A Knock-in approach, using the mCherry tag, enabled the protein to be located during the intra-erythrocytic cycle, showing a presence in the cytoplasm during the trophozoite to schizont stages, and a localised concentration in the nucleus in gametocytes. Finally, immunoprecipitation followed by mass spectrometry analysis enabled us to characterise the PbRpt3 interactome in the parasite during the schizont stage. We confirmed that PbRpt3 belongs to the 19S proteasome complex and observed that this ATPase associates with several proteins known to bind to membrane phospholipids. These observations suggest that PbRpt3 could play a direct role, or indirect, through interacting with partners, in the membrane dynamics of P. berghei

Abstract Adenylyl cyclase (AC; adenylate cyclase or ATP pyrophosphate lyase; E.C. 4.6.1.1) catalyses the formation of cyclic AMP (cAMP), using ATP as substrate. The theoretical topology of all ACs is similar, with both amino- and carboxyl-termini on the cytosolic side, twelve transmembrane domains divided into two groups, and linked with an extended cytosolic loop (1). The catalytic activity and the regulatory elements of AC appear to be concentrated on the cytosolic loop (C1 domain) and the carboxyl-terminal tail (C domain). To date, nine subtypes of mammalian adenylyl cyclases (A Cs) have been successfully cloned (1-15), and a partial cDNA fragment corresponding to a novel AC subtype (type X) has also been identified (16). All ACs are subjected to extensive regulatory signals, including Ca2+, G proteins, protein phosphorylation, and small molecules such as forskolin and adenosine analogues (also known as P-site analogues), as reviewed in refs. 17-19, and summarized in Table 1.

This paper presents the results of statistical and engineering analysis of Loss of Offsite Power (LOOP) events registered in four reviewed databases. The paper includes events registered in IRSN (Institut de Radioprotection et de Sûreté Nucléaire) SAPIDE and GRS (Gesellschaft für Anlagen- und Reaktorsicherheit mbH) VERA database in time period 1992 to 2011. The Nuclear Regulatory Commission (NRC) Licensee Event Reports (LERs) database and the IAEA International Reporting System (IRS) database are screened for the relevant events registered in period 1990 to 2013. In total, 228 relevant events were identified in the IRSN database, 190 in GRS, 120 in LER and 52 in IRS. The data include events registered both during the critical (at power) and shutdown operation of the plants. The identified events were classified considering nine different categories. In the three databases (SAPIDE, VERA, IAEA-IRS) the largest numbers of events are registered for the plant centered category. The largest number of the events in the NRC-LER database is found for switchyard centered events. According to the mode of operation, most events were reported during critical power operation, in all four databases. The “Partial loss of external power” events are the most frequent type of event found in the IRSN and NRC databases while the “Physical loss of electrical busbars” is the main type in the GRS and IAEA databases. The largest number of events in all databases is identified for the switchyard failures followed by the interconnections failures (both lines and transformers). Mainly LOOP event are identified by the fault report in the control room. Electrical deficiency is detected as the main direct cause of events. Environment is registered as the main contributor for the electrical grid deficiency in the French and NRC databases. Electrical failures are dominant contributor to the electrical grid deficiency in the German and IAEA databases. The principal root cause for the LOOP events are human failures with the human errors during test, inspection and maintenance as the largest sub-group. The largest number of the LOOP events resulted in reactor trip followed by the Emergency Diesel Generator (EDG) start. The majority of the reported LOOP events lasted for more than 2 minutes. Main lessons learned from the analysed events and potential actions for decrease of the number of LOOP events are presented.

1.1 Macroeconomic summary Economic recovery has consistently outperformed the technical staff’s expectations following a steep decline in activity in the second quarter of 2020. At the same time, total and core inflation rates have fallen and remain at low levels, suggesting that a significant element of the reactivation of Colombia’s economy has been related to recovery in potential GDP. This would support the technical staff’s diagnosis of weak aggregate demand and ample excess capacity. The most recently available data on 2020 growth suggests a contraction in economic activity of 6.8%, lower than estimates from January’s Monetary Policy Report (-7.2%). High-frequency indicators suggest that economic performance was significantly more dynamic than expected in January, despite mobility restrictions and quarantine measures. This has also come amid declines in total and core inflation, the latter of which was below January projections if controlling for certain relative price changes. This suggests that the unexpected strength of recent growth contains elements of demand, and that excess capacity, while significant, could be lower than previously estimated. Nevertheless, uncertainty over the measurement of excess capacity continues to be unusually high and marked both by variations in the way different economic sectors and spending components have been affected by the pandemic, and by uneven price behavior. The size of excess capacity, and in particular the evolution of the pandemic in forthcoming quarters, constitute substantial risks to the macroeconomic forecast presented in this report. Despite the unexpected strength of the recovery, the technical staff continues to project ample excess capacity that is expected to remain on the forecast horizon, alongside core inflation that will likely remain below the target. Domestic demand remains below 2019 levels amid unusually significant uncertainty over the size of excess capacity in the economy. High national unemployment (14.6% for February 2021) reflects a loose labor market, while observed total and core inflation continue to be below 2%. Inflationary pressures from the exchange rate are expected to continue to be low, with relatively little pass-through on inflation. This would be compatible with a negative output gap. Excess productive capacity and the expectation of core inflation below the 3% target on the forecast horizon provide a basis for an expansive monetary policy posture. The technical staff’s assessment of certain shocks and their expected effects on the economy, as well as the presence of several sources of uncertainty and related assumptions about their potential macroeconomic impacts, remain a feature of this report. The coronavirus pandemic, in particular, continues to affect the public health environment, and the reopening of Colombia’s economy remains incomplete. The technical staff’s assessment is that the COVID-19 shock has affected both aggregate demand and supply, but that the impact on demand has been deeper and more persistent. Given this persistence, the central forecast accounts for a gradual tightening of the output gap in the absence of new waves of contagion, and as vaccination campaigns progress. The central forecast continues to include an expected increase of total and core inflation rates in the second quarter of 2021, alongside the lapse of the temporary price relief measures put in place in 2020. Additional COVID-19 outbreaks (of uncertain duration and intensity) represent a significant risk factor that could affect these projections. Additionally, the forecast continues to include an upward trend in sovereign risk premiums, reflected by higher levels of public debt that in the wake of the pandemic are likely to persist on the forecast horizon, even in the context of a fiscal adjustment. At the same time, the projection accounts for the shortterm effects on private domestic demand from a fiscal adjustment along the lines of the one currently being proposed by the national government. This would be compatible with a gradual recovery of private domestic demand in 2022. The size and characteristics of the fiscal adjustment that is ultimately implemented, as well as the corresponding market response, represent another source of forecast uncertainty. Newly available information offers evidence of the potential for significant changes to the macroeconomic scenario, though without altering the general diagnosis described above. The most recent data on inflation, growth, fiscal policy, and international financial conditions suggests a more dynamic economy than previously expected. However, a third wave of the pandemic has delayed the re-opening of Colombia’s economy and brought with it a deceleration in economic activity. Detailed descriptions of these considerations and subsequent changes to the macroeconomic forecast are presented below. The expected annual decline in GDP (-0.3%) in the first quarter of 2021 appears to have been less pronounced than projected in January (-4.8%). Partial closures in January to address a second wave of COVID-19 appear to have had a less significant negative impact on the economy than previously estimated. This is reflected in figures related to mobility, energy demand, industry and retail sales, foreign trade, commercial transactions from selected banks, and the national statistics agency’s (DANE) economic tracking indicator (ISE). Output is now expected to have declined annually in the first quarter by 0.3%. Private consumption likely continued to recover, registering levels somewhat above those from the previous year, while public consumption likely increased significantly. While a recovery in investment in both housing and in other buildings and structures is expected, overall investment levels in this case likely continued to be low, and gross fixed capital formation is expected to continue to show significant annual declines. Imports likely recovered to again outpace exports, though both are expected to register significant annual declines. Economic activity that outpaced projections, an increase in oil prices and other export products, and an expected increase in public spending this year account for the upward revision to the 2021 growth forecast (from 4.6% with a range between 2% and 6% in January, to 6.0% with a range between 3% and 7% in April). As a result, the output gap is expected to be smaller and to tighten more rapidly than projected in the previous report, though it is still expected to remain in negative territory on the forecast horizon. Wide forecast intervals reflect the fact that the future evolution of the COVID-19 pandemic remains a significant source of uncertainty on these projections. The delay in the recovery of economic activity as a result of the resurgence of COVID-19 in the first quarter appears to have been less significant than projected in the January report. The central forecast scenario expects this improved performance to continue in 2021 alongside increased consumer and business confidence. Low real interest rates and an active credit supply would also support this dynamic, and the overall conditions would be expected to spur a recovery in consumption and investment. Increased growth in public spending and public works based on the national government’s spending plan (Plan Financiero del Gobierno) are other factors to consider. Additionally, an expected recovery in global demand and higher projected prices for oil and coffee would further contribute to improved external revenues and would favor investment, in particular in the oil sector. Given the above, the technical staff’s 2021 growth forecast has been revised upward from 4.6% in January (range from 2% to 6%) to 6.0% in April (range from 3% to 7%). These projections account for the potential for the third wave of COVID-19 to have a larger and more persistent effect on the economy than the previous wave, while also supposing that there will not be any additional significant waves of the pandemic and that mobility restrictions will be relaxed as a result. Economic growth in 2022 is expected to be 3%, with a range between 1% and 5%. This figure would be lower than projected in the January report (3.6% with a range between 2% and 6%), due to a higher base of comparison given the upward revision to expected GDP in 2021. This forecast also takes into account the likely effects on private demand of a fiscal adjustment of the size currently being proposed by the national government, and which would come into effect in 2022. Excess in productive capacity is now expected to be lower than estimated in January but continues to be significant and affected by high levels of uncertainty, as reflected in the wide forecast intervals. The possibility of new waves of the virus (of uncertain intensity and duration) represents a significant downward risk to projected GDP growth, and is signaled by the lower limits of the ranges provided in this report. Inflation (1.51%) and inflation excluding food and regulated items (0.94%) declined in March compared to December, continuing below the 3% target. The decline in inflation in this period was below projections, explained in large part by unanticipated increases in the costs of certain foods (3.92%) and regulated items (1.52%). An increase in international food and shipping prices, increased foreign demand for beef, and specific upward pressures on perishable food supplies appear to explain a lower-than-expected deceleration in the consumer price index (CPI) for foods. An unexpected increase in regulated items prices came amid unanticipated increases in international fuel prices, on some utilities rates, and for regulated education prices. The decline in annual inflation excluding food and regulated items between December and March was in line with projections from January, though this included downward pressure from a significant reduction in telecommunications rates due to the imminent entry of a new operator. When controlling for the effects of this relative price change, inflation excluding food and regulated items exceeds levels forecast in the previous report. Within this indicator of core inflation, the CPI for goods (1.05%) accelerated due to a reversion of the effects of the VAT-free day in November, which was largely accounted for in February, and possibly by the transmission of a recent depreciation of the peso on domestic prices for certain items (electric and household appliances). For their part, services prices decelerated and showed the lowest rate of annual growth (0.89%) among the large consumer baskets in the CPI. Within the services basket, the annual change in rental prices continued to decline, while those services that continue to experience the most significant restrictions on returning to normal operations (tourism, cinemas, nightlife, etc.) continued to register significant price declines. As previously mentioned, telephone rates also fell significantly due to increased competition in the market. Total inflation is expected to continue to be affected by ample excesses in productive capacity for the remainder of 2021 and 2022, though less so than projected in January. As a result, convergence to the inflation target is now expected to be somewhat faster than estimated in the previous report, assuming the absence of significant additional outbreaks of COVID-19. The technical staff’s year-end inflation projections for 2021 and 2022 have increased, suggesting figures around 3% due largely to variation in food and regulated items prices. The projection for inflation excluding food and regulated items also increased, but remains below 3%. Price relief measures on indirect taxes implemented in 2020 are expected to lapse in the second quarter of 2021, generating a one-off effect on prices and temporarily affecting inflation excluding food and regulated items. However, indexation to low levels of past inflation, weak demand, and ample excess productive capacity are expected to keep core inflation below the target, near 2.3% at the end of 2021 (previously 2.1%). The reversion in 2021 of the effects of some price relief measures on utility rates from 2020 should lead to an increase in the CPI for regulated items in the second half of this year. Annual price changes are now expected to be higher than estimated in the January report due to an increased expected path for fuel prices and unanticipated increases in regulated education prices. The projection for the CPI for foods has increased compared to the previous report, taking into account certain factors that were not anticipated in January (a less favorable agricultural cycle, increased pressure from international prices, and transport costs). Given the above, year-end annual inflation for 2021 and 2022 is now expected to be 3% and 2.8%, respectively, which would be above projections from January (2.3% and 2,7%). For its part, expected inflation based on analyst surveys suggests year-end inflation in 2021 and 2022 of 2.8% and 3.1%, respectively. There remains significant uncertainty surrounding the inflation forecasts included in this report due to several factors: 1) the evolution of the pandemic; 2) the difficulty in evaluating the size and persistence of excess productive capacity; 3) the timing and manner in which price relief measures will lapse; and 4) the future behavior of food prices. Projected 2021 growth in foreign demand (4.4% to 5.2%) and the supposed average oil price (USD 53 to USD 61 per Brent benchmark barrel) were both revised upward. An increase in long-term international interest rates has been reflected in a depreciation of the peso and could result in relatively tighter external financial conditions for emerging market economies, including Colombia. Average growth among Colombia’s trade partners was greater than expected in the fourth quarter of 2020. This, together with a sizable fiscal stimulus approved in the United States and the onset of a massive global vaccination campaign, largely explains the projected increase in foreign demand growth in 2021. The resilience of the goods market in the face of global crisis and an expected normalization in international trade are additional factors. These considerations and the expected continuation of a gradual reduction of mobility restrictions abroad suggest that Colombia’s trade partners could grow on average by 5.2% in 2021 and around 3.4% in 2022. The improved prospects for global economic growth have led to an increase in current and expected oil prices. Production interruptions due to a heavy winter, reduced inventories, and increased supply restrictions instituted by producing countries have also contributed to the increase. Meanwhile, market forecasts and recent Federal Reserve pronouncements suggest that the benchmark interest rate in the U.S. will remain stable for the next two years. Nevertheless, a significant increase in public spending in the country has fostered expectations for greater growth and inflation, as well as increased uncertainty over the moment in which a normalization of monetary policy might begin. This has been reflected in an increase in long-term interest rates. In this context, emerging market economies in the region, including Colombia, have registered increases in sovereign risk premiums and long-term domestic interest rates, and a depreciation of local currencies against the dollar. Recent outbreaks of COVID-19 in several of these economies; limits on vaccine supply and the slow pace of immunization campaigns in some countries; a significant increase in public debt; and tensions between the United States and China, among other factors, all add to a high level of uncertainty surrounding interest rate spreads, external financing conditions, and the future performance of risk premiums. The impact that this environment could have on the exchange rate and on domestic financing conditions represent risks to the macroeconomic and monetary policy forecasts. Domestic financial conditions continue to favor recovery in economic activity. The transmission of reductions to the policy interest rate on credit rates has been significant. The banking portfolio continues to recover amid circumstances that have affected both the supply and demand for loans, and in which some credit risks have materialized. Preferential and ordinary commercial interest rates have fallen to a similar degree as the benchmark interest rate. As is generally the case, this transmission has come at a slower pace for consumer credit rates, and has been further delayed in the case of mortgage rates. Commercial credit levels stabilized above pre-pandemic levels in March, following an increase resulting from significant liquidity requirements for businesses in the second quarter of 2020. The consumer credit portfolio continued to recover and has now surpassed February 2020 levels, though overall growth in the portfolio remains low. At the same time, portfolio projections and default indicators have increased, and credit establishment earnings have come down. Despite this, credit disbursements continue to recover and solvency indicators remain well above regulatory minimums. 1.2 Monetary policy decision In its meetings in March and April the BDBR left the benchmark interest rate unchanged at 1.75%.