Different Regulations of ROM2 and LRG1 Expression by Ccr4, Pop2, and Dhh1 in the Saccharomyces cerevisiae Cell Wall Integrity Pathway

Ccr4, a component of the Ccr4-Not cytoplasmic deadenylase complex, is known to be required for the cell wall integrity (CWI) pathway in the budding yeast . However, it is not fully understood how Ccr4 and other components of the Ccr4-Not complex regulate the CWI pathway. Previously, we showed that Ccr4 functions in the CWI pathway together with Khd1 RNA binding protein. Ccr4 and Khd1 modulate a signal from Rho1 small GTPase in the CWI pathway by regulating the expression of mRNA and mRNA, encoding a guanine nucleotide exchange factor (GEF) and a GTPase-activating protein (GAP) for Rho1, respectively. Here we examined the possible involvement of the gene encoding a subunit of the Ccr4-Not complex and the gene encoding a DEAD box RNA helicase that associates with the Ccr4-Not complex in the regulation of and expression. Neither mRNA level nor Rom2 function was impaired by or mutation. The mRNA level was increased in and mutants, as well as the mutant, and the growth defects caused by and mutations were suppressed by mutation. Our results suggest that expression is regulated by Ccr4 together with Pop2 and Dhh1 and that expression is regulated by Khd1 and Ccr4, but not by Pop2 and Dhh1. Thus, Rho1 activity in the CWI pathway is precisely controlled by modulation of the mRNA levels for Rho1-GEF Rom2 and Rho1-GAP Lrg1. We find here that Ccr4, Pop2, and Dhh1 modulate the levels of mRNAs for specific Rho1 regulators, Rom2 and Lrg1. In budding yeast, Rho1 activity is tightly regulated both temporally and spatially. It is anticipated that Ccr4, Pop2, and Dhh1 may contribute to the precise spatiotemporal control of Rho1 activity by regulating expression of its regulators temporally and spatially. Our finding on the roles of the components of the Ccr4-Not complex in yeast would give important information for understanding the roles of the evolutionary conserved Ccr4-Not complex.