Fig. 6

Regulation of pro-growth genes by Sumo. a, in the presence of sufficient nutrients, TORC1 and Ubc9 in transcription of pro-growth genes like RPGs and tRNA genes. TORC1 increases phosphorylation of Sfp1 and Ifh1, leading to their recruitment to PRG promoters. Ubc9 sumoylates Rap1, which enhances recruitment of TFIID to RPGs. Ubc9 also sumoylates RNAPIII components, which most likely is required for efficient tRNA transcription. TORC1 increases phosphorylation of Maf1, resulting in its nuclear exclusion. b, During nutrient stress TORC1 is inactive, leading to dephosphorylation of Sfp1 and Ifh1, which are then released from RPG promoters. Maf1 also becomes dephosphorylated, resulting in its nuclear entry where it binds and inhibits RNAPIII. At least in mammals Maf1 is also sumoylated, which contributes to its repressive effect on RNAPIII. Whether this also occurs in yeast is unknown