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Figure 2 | Cell Division

Figure 2

From: Rim15 and the crossroads of nutrient signalling pathways in Saccharomyces cerevisiae

Figure 2

Integration of nutrient signals by Rim15. Rim15 activity is regulated by at least four nutrient-regulated protein kinases. Cytoplasmic Rim15, anchored through its binding to the 14-3-3 proteins, is kept inactive through PKA-mediated phosphorylation. TORC1 inactivation results in dephosphorylation of phospho-Thr1075 (indicated with P) in Rim15 and concomitant translocation of Rim15 to the nucleus where it escapes further PKA-mediated inhibition (as Bcy1 inhibits PKA activity in the nucleus). Also the Pho85-Pho80 kinase is involved in phosphorylation of Thr1075 in Rim15, thereby promoting cytoplasmic retention of nuclear exported Rim15. The mechanism by which Sch9 inhibits the nuclear localisation of Rim15 is not known. Active nuclear Rim15 regulates entry into the stationary (G0) phase via regulation of the Msn2,4 and Gis1 transcription factors. Msn2/4 regulate expression of stress responsive (STRE) genes while Gis1 induces transcription of post-diauxic shift (PDS) genes. Active Rim15 also initiates an autophosphorylation process (illustrated by the double line around Rim15) which stimulates its nuclear export via Msn5. See text for details.

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