Figure 7.

A proposed model shows that Rph1 coordinates transcription of RPGs and rRNAs to control cell growth under nutrient stress conditions. With nutrient stress to inactivate TORC1 and Sch9, phosphorylated Rim15 is translocated to nucleus and catalyzes Rph1 phosphorylation, which releases the majority of Rph1 from transcribed regions of RPGs and 35S rDNAs, thereby maintaining long-term cell survival. Under the same stress condition, complete absence of RPH1 leads to about 1.5-fold increase of expression levels of RPGs and 35S rRNAs compared to WT cells, which further promotes ribosome biogenesis and cell growth.