Cdk and the anillin homolog Bud4 define a new pathway regulating septin organization in yeast

In budding yeast, the cortical structure formed by the septins is remodeled at the onset of mitotic exit and delineates a specialized compartment dedicated to cytokinesis. How this septin function is spatially and timely regulated remains poorly understood. In this study, we report a role of the anillin-like protein Bud4 in the formation and the disassembly of the double ring structure formed by the septins at the time of cytokinesis. Bud4 acts with Bud3 in this pathway and in parallel with septin phosphorylation by the p21-activated kinase Cla4 and the septin-dependent kinase Gin4. In addition, we show that the function of Bud4 is regulated by the cyclin-dependent protein kinase Cdk1, the master regulator of cell cycle progression. This result suggests that the Cdks, or a locally specific pool of the kinase, may have a role past mitotic exit.