The Ccr4-Pop2-NOT mRNA Deadenylase Contributes to Septin Organization in Saccharomyces cerevisiae

In yeast, assembly of the septins at the cell cortex is required for a series of key cell cycle events: bud-site selection, the morphogenesis and mitotic exit checkpoints, and cytokinesis. Here we establish that the Ccr4-Pop2-NOT mRNA deadenylase contributes to septin organization. mRNAs encoding regulators of septin assembly (Ccd42, Cdc24, Rga1, Rga2, Bem3, Gin4, Cla4 and Elm1) presented with short poly(A) fails at steady state in wild-type (wt.) cells, suggesting their translation could be restricted by deadenylation. Deadenylation of septin regulators was dependent oil the major cellular mRNA deadenylase Ccr4-Pop2-NOT, whereas die alternative deadenylase Pan2 played it minor role. Consistent with deadenylation of septin regulators being important for function, deletion of deadenylase subunits CCR4 or POP2, but not PAN2, resulted in septin morphology defects (e.g., ectopic bud-localized septin rings), particularly upon activation of the Cdc28-inhibitory kinase Swe1. Aberrant septin staining was also observed in the deadenylase-dead ccr4-1 mutant, demonstrating the deadenylase activity of Cct-4-Pop2 is required. Moreover, ccr4 Delta, pop2 Delta, and ccr4-1 mutants showed aberrant cell morphology previously observed in septin assembly mutants and exhibited genetic interactions with mutations that compromise septin assembly (shs1 Delta, cla4 Delta, elm Delta, and gin4 Delta). Mutations in the Not subunits of Ccr4-Pop2-NOT, which are thought to predominantly function in transcriptional control, also resulted in septin organization defects. Therefore, both mRNA deadenylase and transcriptional functions of Ccr4-Pop2-NOT contribute to septin organization in yeast.