Transcription by RNA polymerase III: insights into mechanism and regulation

Abstract

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 phenotypes and cell physiology

“…The opposite response was generally seen upon Maf1 knockdown although not all of the tested tRNAs were affected. (This may reflect the relative resistance of some tRNA genes to Maf1-mediated repression as found recently in mammalian cells and yeast [40,41]). Overexpression of Maf1 also reduced the expression of a surprisingly large number of Pol II-transcribed genes.…”

The Maize Imprinted Gene Floury3 Encodes a PLATZ Protein Required for tRNA and 5S rRNA Transcription through Interaction with RNA Polymerase III

“…RNAPIII is responsible for the transcription of short noncoding RNAs, such as tRNAs and 5S rRNA (Turowski and Tollervey, 2016). In addition to RNAPIII, TFIIIA, TFIIIB, and TFIIIC are also part of the RNAPIII transcription machinery, forming the preinitiation complex and recruiting RNAPIII to the promoter for transcription initiation (Dieci et al, 2013;Male et al, 2015;Turowski and Tollervey, 2016).…”

“…In addition to RNAPIII, TFIIIA, TFIIIB, and TFIIIC are also part of the RNAPIII transcription machinery, forming the preinitiation complex and recruiting RNAPIII to the promoter for transcription initiation (Dieci et al, 2013;Male et al, 2015;Turowski and Tollervey, 2016). Therefore, the maize homolog of the TFIIIC subunit TFC1 (GRMZM2G053008) was cloned.…”

“…RNAPI is responsible for the transcription of large rRNAs (in plants being 18 and 25S rRNAs); RNAPII synthesizes mRNAs of protein-coding genes; and RNAPIII transcribes many short noncoding RNAs, such as tRNAs, 5S rRNA, and 7SL RNA (Turowski and Tollervey, 2016). Additionally, plant-specific RNAP IV and V transcribe small interfering RNAs for RNA-mediated DNA methylation (Zhou and Law, 2015).…”

“…Moreover, highly abundant ribosomal proteins, tRNAs and rRNAs, are also required to achieve high-efficiency functioning of the protein translation machinery. The RNA polymerase III (RNAPIII) complex is specialized for the transcription of tRNAs and other small noncoding RNAs including 5S rRNA, U6 spliceosomal RNA, and 7SL RNA (Nikitina et al, 2011;Nielsen et al, 2013;Turowski and Tollervey, 2016). In yeast, the RNAPIII transcription complex involves RNAPIII, a 17-subunit enzyme, and three transcription factors (TFIIIA, TFIIIB, and TFIIIC) (Acker et al, 2013).…”