Isolation and characterization of y4 adenylate cyclase and cAMP-deper (Saccharomyces cerevisiae/cAMP/cAMP-binding protein/suppressic

Mutants of Saccharomyces cerevisiae that re- quire cAMP for growth have been isolated. Some of the mutants isolated were deficient in adenylate cyclase activity and mapped at a locus, cyri, located near the centromere of chromosome X. Growth of cells carrying the cyri mutation was arrested at the Gi phase of the yeast cell cycle in the absence of cAMP.' The cyri mutation was suppressed by a secondary mutation designated beyl. The bcyl mutation bypassed the need for cAMP for growth. The bcyl mutants had extremely low levels of cAMP-binding pro- tein and cAMP-dependent protein kinase but produced a high level of cAMP-independent protein kinase. The results indicate that cAMP is an essential factor for yeast cells to proceed through the cell cycle via the activation of protein kinase.