Role of Plc1p in regulation of Mcm1p-dependent genes.

In budding yeasts, phosphoinositide-specific phospholipase C (Plc1p encoded by PLC1 gene) and several inositol polyphosphate kinases represent a nuclear pathway for synthesis of inositol polyphosphates (InsPs), which are involved in several aspects of DNA and RNA metabolism, including transcriptional regulation. Plc1p-produced inositol trisphosphate (InsP(3)) is phosphorylated by Ipk2p/Arg82p to yield InsP(4)/InsP(5). Ipk2p/Arg82p is also a component of ArgR-Mcm1p complex that regulates transcription of genes involved in arginine metabolism. The role of Ipk2p/Arg82p in this complex is to stabilize the essential MADS box protein Mcm1p. Consequently, ipk2Delta cells display reduced levels of Mcm1p and attenuated expression of Mcm1p-dependent genes. Because plc1Delta cells display aberrant expression of several groups of genes, including genes involved in stress response, the objective of this study was to determine whether Plc1p also affects expression of Mcm1p-dependent genes. Here we report that not only ipk2Delta, but also plc1Delta cells display decreased expression of Mcm1p-dependent genes. However, Plc1p is not involved in stabilization of Mcm1p and affects transcription of Mcm1p-dependent genes by a different mechanism, probably involving regulation of chromatin remodeling complexes.