A zinc finger protein required for stationary phase viability in fission yeast

Yeast cells exit the cell cycle and enter a metabolically inert stationary phase when starved for nutrients essential for normal proliferation. We have cloned a novel gene named rsv1+ (required for stationary phase viability) that is essential for fission yeast cell viability in a stationary phase induced by glucose starvation. rsv1+ encodes a 47 kDa protein with two zinc finger motifs that are partially homologous with Aspergillus nidulans CreA, Saccharomyces cerevisiae Mig1 and mammalian 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 by ectopic expression of rsv1+. Thus, poor induction of rsv1+ is at least partially responsible for the viability loss. Analysis also showed that cells need to receive starvation signals before entry into the stationary phase in order to maintain viability in a glucose-poor environment.