title: Novel layers of RNA polymerase III control affecting tRNA gene transcription in eukaryotes.
abstract: RNA polymerase III (Pol III) transcribes a limited set of short genes in eukaryotes producing abundant small RNAs, mostly tRNA. The originally defined yeast Pol III transcriptome appears to be expanding owing to the application of new methods. Also, several factors required for assembly and nuclear import of Pol III complex have been identified recently. Models of Pol III based on cryo-electron microscopy reconstructions of distinct Pol III conformations reveal unique features distinguishing Pol III from other polymerases. Novel concepts concerning Pol III functioning involve recruitment of general Pol III-specific transcription factors and distinctive mechanisms of transcription initiation, elongation and termination. Despite the short length of Pol III transcription units, mapping of transcriptionally active Pol III with nucleotide resolution has revealed strikingly uneven polymerase distribution along all genes. This may be related, at least in part, to the transcription factors bound at the internal promoter regions. Pol III uses also a specific negative regulator, Maf1, which binds to polymerase under stress conditions; however, a subset of Pol III genes is not controlled by Maf1. Among other RNA polymerases, Pol III machinery represents unique features related to a short transcript length and high transcription efficiency.
authors.affiliation: Department of Genetics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Leśniewska
authors.affiliation: Department of Genetics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland magda@ibb.waw.pl.
authors.forename: Magdalena
authors.identifier: 0000-0002-1545-0691
authors.initials: M
authors.lastname: Boguta
mesh_terms: D056890:Eukaryota / Q000201:enzymology / Q000235:genetics*; D011487:Protein Conformation; D012320:RNA Polymerase III / Q000737:chemistry / Q000378:metabolism*; D012343:RNA, Transfer / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D012097:Repressor Proteins; D012343:RNA, Transfer; D012320:RNA Polymerase III
keywords: Pol III; TFIIIC; polymerase assembly; tRNA; transcription elongation; transcription termination read-through