Regulation of tRNA synthesis by posttranslational modifications of RNA polymerase III subunits

RNA polymerase III (RNAPIII) transcribes tRNA genes, 5S RNA as well as a number of other non-coding RNAs. Because transcription by RNAPIII is an energy-demanding process, its activity is tightly linked to the stress levels and nutrient status of the cell. Multiple signaling pathways control RNAPIII activity in response to environmental cues, but exactly how these pathways regulate RNAPIII is still poorly understood. One major target of these pathways is the transcriptional repressor Maf1, which inhibits RNAPIII activity under conditions that are detrimental to cell growth. However, recent studies have found that the cell can also directly regulate the RNAPIII machinery through phosphorylation and sumoylation of RNAPIII subunits. In this review we summarize post-translational modifications of RNAPIII subunits that mainly have been identified in large-scale proteomics studies, and we highlight several examples to discuss their relevance for regulation of RNAPIII.