A ZINC-FINGER PROTEIN REQUIRED FOR STATIONARY-PHASE VIABILITY IN FISSION YEAST

Yeast cells exit the cell cycle and enter a metabolically inert statio nary phase when starved for nutrients essential for normal proliferati on. We have cloned a novel gene named rsv1(+) (required for stationary phase viability) that is essential for fission yeast cell viability i n a stationary phase induced by glucose starvation. rsv1(+) encodes a 47 kDa protein with two zinc finger motifs that are partially homologo us with Aspergillus nidulans CreA, Saccharomyces cerevisiae Mig1 and m ammalian EGR-1/NGFI-A. Cells deleted for rsv1(+) are unable to survive glucose starvation. Transcription of rsv1(+) is negatively regulated by the cAMP pathway and induced by glucose starvation. Cells with the constitutively activated cAMP pathway are known to lose viability when grown to confluence or when starved for glucose. These cells are poor in rsv1(+) induction and their viability loss is largely suppressed b y ectopic expression of rsv1(+). Thus, poor induction of rsv(1+) is at least partially responsible for the viability loss. Analysis also sho wed that cells need to receive starvation signals before entry into th e stationary phase in order to maintain viability in a glucose-poor en vironment.