YEAST BCY1 MUTANTS WITH STATIONARY-PHASE SPECIFIC DEFECTS

Entry into the stationary phase requires the yeast BCY1 gene, which en codes the regulatory subunit of the cAMP-dependent protein kinase (cAP K). New bcy1 mutants, constructed by in vitro mutagenesis of the 3'-re gion encoding the cAMP-binding domains, were classified as early or la te-acting mutants based on viability studies. The late-acting bcy1 mut ants accumulated fewer stationary phase-specific Bcy1p isoforms and ha d decreased cAPK activity. This late-acting class is novel and dies af ter 7 days in culture, later than two previously reported stationary p hase mutants, ubi4 and ard1.