Suppression mechanism of the calcium sensitivity in Saccharomyces cerevisiae ptp2Δmsg5Δ double disruptant involves a novel HOG-independent function of Ssk2, transcription factor Msn2 and the protein kinase A component Bcy1

In Saccharomyces cerevisiae, disruption of both protein phosphatase genes, PTP2 and MSG5, causes calcium sensitivity while additional disruption of protein kinase genes BCK1, MKK1, SLT2, MCK1, YAK1 and SSK2 confers calcium tolerance. Although the roles of BCK1, MKK1 and SLT2 have been characterized recently, the mechanism of suppression of the calcium sensitivity by SSK2 disruption is poorly understood. In this study, genetic analysis revealed a novel, high osmolarity glycerol (HOG)-independent suppressor function of Ssk2 in relation to the Ptp2 and Msg5-mediated calcium signaling. Through microarray analysis, we identified 19 genes with distinct pattern of expression that is likely involved in the calcium sensitive phenotype of the ptp2Δmsg5Δ double disruptant. Furthermore, we found msn2Δ and bcy1Δ as suppressors of the calcium sensitive phenotype. Our results suggest the interrelationship of a HOG-independent function of Ssk2, transcription factor Msn2, protein kinase A-related protein Bcy1 and 19 rise and fall genes as responsible for the suppression mechanism of the ptp2Δmsg5Δ double disruptant by ssk2Δ disruption.