Maf1 was the first protein discovered to regulate polymerase III RNA in yeast and because it is evolutionarily conserved, a Maf1 ortholog also serves to restrain transcription in mouse and human cells. Understanding the mechanism of the regulation has been made possible by recent studies showing that Maf1 is a nuclear/cytoplasmic protein whose subcellular distribution and hence negative regulation of Pol III transcription is mediated by the nutrient-sensing signaling pathways, TOR and RAS. Under stress conditions and during growth in a nonfermentable carbon source Maf1 is dephosphorylated and imported to the nucleus. In its non-phosphorylated form, Maf1 interacts with the polymerase III transcription machinery. Phosphorylation serves to locate Maf1 to the cytoplasm under favorable growth conditions, thereby preventing it from non-negatively regulating polymerase III when high levels of tRNA transcription are required. Relocation of Maf1 to the cytoplasm is dependent on Msn5, a carrier responsible for export of several other phosphoproteins out of the nucleus. The absence of Maf1-mediated control of tRNA synthesis impairs yeast viability in nonfermentable carbon sources. Moreover, in cells grown in a nonfermentable carbon source, Maf1 regulates the levels of different tRNAs to various extents. This differential regulation may contribute to the physiological role of Maf1.

• PMID: 18560610
• PubMed
• PubTator

Reference Type

Journal Article | Research Support, Non-U.S. Gov't | Review

Authors

Cieśla M, Boguta M

Primary Lit For

Additional Lit For

Review For

RPC17 | RPC25 | PPH22 | RPC10 | PKC1 | PPH3 | RPB5 | PPH21 | BCY1 | MAF1 | RPC37 | ... Show allRPC53 | BRF1 | RPC11 | RPC40 | RPC19 | RPO31 | RPO26 | RET1 | RPB10 | RPB8 | BDP1 | RPC82 | SPT15 | RPC34 | CDC25 | RAS2 | RPC31 Show fewer