Maf1-mediated regulation of yeast RNA polymerase III is correlated with CCA addition at the 3' end of tRNA precursors

In eukaryotic cells tRNA synthesis is negatively regulated by the protein Maf1, conserved from yeast to humans. Maf1 from yeast Saccharomyces cerevisiae mediates repression of trna transcription when cells are transferred from medium with glucose to medium with glycerol, a non-fermentable carbon source. The strain with deleted gene encoding Maf1 (maf1Δ) is viable but accumulates tRNA precursors. In this study tRNA precursors were analysed by RNA-Seq and Northern hybridization in wild type strain and maf1Δ mutant grown in glucose medium or upon shift to repressive conditions. A negative effect of maf1Δ mutant on the addition of the auxiliary CCA nucleotides to the 3′ end of pre-tRNAs was observed in cells shifted to unfavourable growth conditions. This effectwas reduced by overexpression of the yeast CCA1 gene encoding ATP(CTP):tRNA nucleotidyltransferase. The CCA sequence at the 3′ end is important for export of tRNA precursors from the nucleus and essential for tRNA charging with amino acids. Data presented here indicate that CCA-addition to intron-containing end-processed tRNA precursors is a limiting step in tRNA maturation when there is no Maf1 mediated RNA polymerase III (Pol III) repression. The correlation between CCA synthesis and Pol III regulation by Maf1 could be important in coordination of tRNA transcription, processing and regulation of translation

Function of TFIIIC, RNA polymerase III initiation factor, in activation and repression of tRNA gene transcription

Transcription of transfer RNA genes by RNA polymerase III (Pol III) is controlled by general factors, TFIIIB and TFIIIC, and a negative regulator, Maf1. Here we report the interplay between TFIIIC and Maf1 in controlling Pol III activity upon the physiological switch of yeast from fermentation to respiration. TFIIIC directly competes with Pol III for chromatin occupancy as demonstrated by inversely correlated tDNA binding. The association of TFIIIC with tDNA was stronger under unfavorable respiratory conditions and in the presence of Maf1. Induction of tDNA transcription by glucose-activated protein kinase A (PKA) was correlated with the down-regulation of TFIIIC occupancy on tDNA. The conditions that activate the PKA signaling pathway promoted the binding of TFIIIB subunits, Brf1 and Bdp1, with tDNA, but decreased their interaction with TFIIIC. Association of Brf1 and Bdp1 with TFIIIC was much stronger under repressive conditions, potentially restricting TFIIIB recruitment to tDNA and preventing Pol III recruitment. Altogether, we propose a model in which, depending on growth conditions, TFIIIC promotes activation or repression of tDNA transcription

Transcription by RNA polymerase III: insights into mechanism and regulation

The highly abundant, small stable RNAs that are synthesized by RNA polymerase III (RNAPIII) have key functional roles, particularly in the protein synthesis apparatus. Their expression is metabolically demanding, and is therefore coupled to changing demands for protein synthesis during cell growth and division. Here, we review the regulatory mechanisms that control the levels of RNAPIII transcripts and discuss their potential physiological relevance. Recent analyses have revealed differential regulation of tRNA expression at all steps on its biogenesis, with significant deregulation of mature tRNAs in cancer cells

Maf1-mediated repression of RNA polymerase III transcription inhibits tRNA degradation via RTD pathway

tRNA precursors, which are transcribed by RNA polymerase III, undergo end-maturation, splicing and base modifications. Hypomodified tRNAs, such as tRNAVal(AAC), lacking 7-methylguanosine and 5-methylcytidine modifications, are subject to degradation by a rapid tRNA decay pathway. Here we searched for genes which, when overexpressed, restored stability of tRNAVal(AAC) molecules in a modification–deficient trm4Δtrm8Δ mutant. We identified TEF1 and VAS1, encoding elongation factor eEF1A and valyl-tRNA synthetase respectively, which likely protect hypomodified tRNAVal(AAC) by direct interactions. We also identified MAF1 whose product is a general negative regulator of RNA polymerase III. Expression of an Maf1-7A mutant that constitutively repressed RNA polymerase III transcription resulted in increased stability of hypomodified tRNAVal(AAC). Strikingly, inhibition of tRNA transcription in a Maf1-independent manner, either by point mutation in RNA polymerase III subunit Rpc128 or decreased expression of Rpc17 subunit, also suppressed the turnover of the hypomodified tRNAVal(AAC). These results support a model where inhibition of tRNA transcription leads to stabilization of hypomodified tRNAVal(AAC) due to more efficient protection by tRNA-interacting proteins

Maf1, repressor of RNA polymerase III, indirectly affects tRNA processing

Maf1 is negative regulator of RNA polymerase III in yeast. We observed high levels of both primary transcript and end-matured, intron-containing pre-tRNAs in the maf1∆ strain. This pre-tRNA accumulation could be overcome by transcription inhibition, arguing against a direct role of Maf1 in tRNA maturation and suggesting saturation of processing machinery by the increased amounts of primary transcripts. Saturation of the tRNA exportin, Los1, is one reason why end-matured intron-containing pre-tRNAs accumulate in maf1∆ cells. However, it is likely possible that other components of the processing pathway are also limiting when tRNA transcription is increased. According to our model, Maf1- mediated transcription control and nuclear export by Los1 are two major stages of tRNA biosynthesis that are regulated by environmental conditions in a coordinated manner

Canute the Great and his connections with the Slavic area

Poniższa praca licencjacka prezentuje zagadnienia związane z panującym w 1. połowie XI wieku Kanutem Wielkim, królem Anglii, Danii i Norwegii. W pracy przedstawiono zarówno biografię króla, jak i stosunki polityczne oraz więzi rodzinne łączące jego osobę z obszarem Słowiańszczyzny.This under mentioned thesis presents issues bound up with reigning in first half of XI century Canute the Great, the king of England, Denmark and Norway. Thesis introduces the king's biography as well as political relations and family connections joining king Canute with Slavian lands

Selected ports of trade on the southern coast of the Baltic Sea in the Early Middle Ages.

We wczesnym średniowieczu na południowym wybrzeżu Morza Bałtyckiego powstaje szereg ośrodków rzemieślniczo handlowych. Część z nich zostaje założona przez obcych etnicznie przybyszy – głównie Skandynawów, część dzięki dogodnej koniunkturze gospodarczej rozwija się, ewoluując od niewielkich osad w bogate emporia handlowe. Cechą wspólną tych ośrodków jest ich dogodne położenie w pobliżu ważnych szlaków handlowych oraz posiadanie rozbudowanych portów, umożliwiających zamorski handel dalekosiężny. Wyróżnione w pracy ośrodki lokalizuje się na Pomorzu Zachodnim ( Szczecin, Wolin, Kołobrzeg), oraz Pomorzu Wschodnim ( Puck, Gdańsk, Truso). W czasie prac archeologicznych odkryto nie tylko relikty portów i nabrzeży, ale również ulice, konstrukcje obronne, relikty domostw i warsztatów rzemieślniczych.A number of early trading centers is created on the southern coast of the Baltic Sea in the Early Middle Ages. Some of them are founded by foreigners – mainly by people from Scandinavia. The others, due to favorable economic conditions, evolve from small villages to rich trading emporiums. The common feature of these trading centers is a convenient location and possession of well-developed seaports, which enable overseas long-distance trade. Centers which are highlighted in this thesis regard those located in West Pomerania (Szczecin, Wolin, Kołobrzeg ) and those in East Pomerania ( Puck, Gdańsk, Truso). During archaeological excavations not only the relics of ports and wharves were discovered, but also streets, defensive structures, buildings and craft workshops

Settlement of Kielce in the Early-Medieval Ages.

Poniższa praca licencjacka opisuje zagadnienia związane z najdawniejszymi dziejami miasta Kielce. Zawiera osobne rozdziały, w których przedstawione zostały źródła pisane do najstarszej historii Kielc oraz przegląd najważniejszych badań i stanowisk archeologicznych pochodzących z okresu średniowiecza a realizowanych na terenie miasta. Autor skupia się głównie na zagadnieniu średniowiecznej, przedlokacyjnej, zrekonstruowanej przez archeologa Janusza Kuczyńskiego osady, rozlokowanej wokół kościoła św. Wojciecha oraz ulic IX Wieków Kielc, Warszawskiej i Bodzentyńskiej. W osobnym rozdziale przedstawione zostały początki istnienia kościoła św. Wojciecha oraz kolegiaty pod wezwaniem Najświętszej Marii Panny na Wzgórzu Zamkowym. Przedyskutowana została również kwestia translokacji miasta, możliwa do uchwycenia dzięki pracom archeologicznym na kieleckim rynku w 2010 roku jak i data lokacji miasta, która od lat stanowi kwestię sporną i niemożliwą do jednoznacznego ustalenia z powodu braku informacji w źródłach pisanych.This under mentioned BA thesis describes a issues related to the oldest history of Kielce. The thesis contains three separated chapters in which are the sources of the remotest written history of Kielce and the review of the most important research and archaeological sites from the medieval period, accomplished on the town premises. The author focuses mainly on the issue of the medieval settlement which was reconstructed by an archaeologist Janusz Kuczyński and deployed around the St. Albertus's Church , and streets: IX Wieków Kielc, Warszawska and Bodzentyńska. The separated chapter delineates the beginnings of the St. Albertus's Church and collegiate church dedicated to Virgin Mary on Castle's hill.Discussed was also an issue of translocation of the town, which is possible to catch owning to an archeological works on Kielce's market in 2010 and date of location of the city, which for years is a debatable affair and impossible to unequivocal adjudication due to lack of information in the written sources

Functional and physical interactions of Krr1p, a Saccharomyces cerevisiae nucleolar protein.

The Krr1 protein of Saccharomyces cerevisiae is involved in processing of pre-rRNA and assembly of pre-ribosomal 40S subunits. To further investigate the function of Krr1p we constructed a conditional cold sensitive mutant krr1-21, and isolated seven genes from Schizosaccharomyces pombe whose products suppressed the cold sensitive phenotype of krr1-21 cells. Among the multicopy suppressors we found genes coding for translation elongation factor EF-1α, a putative ribose methyltransferase and five genes encoding ribosomal proteins. Using the tandem affinity purification (TAP) method we identified thirteen S. cerevisiae ribosomal proteins interacting with Krr1p. Taken together, these results indicate that Krr1p interacts functionally as well as physically with ribosomal proteins. Northern blot analysis revealed that changes in the level of krr1-21 mRNA were accompanied by similar changes in the level of mRNAs of genes encoding ribosomal proteins. Thus, Krr1p and the genes encoding ribosomal proteins it interacts with seem to be coordinately regulated at the level of transcription