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 tRNA(Val(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 tRNA(Val(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 tRNA(Val(AAC)) by direct interactions. We also identified MAF1 whose product is a general negative regulator of RNA polymerase III. Expression of a Maf1-7A mutant that constitutively repressed RNA polymerase III transcription resulted in increased stability of hypomodified tRNA(Val(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 tRNA(Val(AAC)). These results support a model where inhibition of tRNA transcription leads to stabilization of hypomodified tRNA(Val(AAC)) due to more efficient protection by tRNA-interacting proteins.
Institute of Biotechnology, Faculty of Chemistry, Warsaw University of Technology, 00-664 Warsaw, Poland.
Tomasz W
TW
Turowski
Iwona
I
Karkusiewicz
Justyna
J
Kowal
Magdalena
M
Boguta
D015536:Down-Regulation / Q000235:genetics; D015966:Gene Expression Regulation, Fungal; D015723:Gene Library; D053858:Metabolic Networks and Pathways / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D050505:Mutant Proteins / Q000502:physiology; D030781:Organisms, Genetically Modified; D010957:Plasmids / Q000235:genetics; D012320:RNA Polymerase III / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics / Q000502:physiology; D020871:RNA Stability / Q000235:genetics*; D012343:RNA, Transfer / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic / Q000235:genetics; D014162:Transfection
C104954:MAF1 protein, S cerevisiae; D050505:Mutant Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D012343:RNA, Transfer; D012320:RNA Polymerase III