Regulation of cytokinesis by the Elm1 protein kinase in Saccharomyces cerevisiae

A Saccharomyces cerevisiae mutant unable to grow in a cdc28-1N background w as isolated and shown to be affected in the ELM1 gene. Elm1 is a protein ki nase, thought to be a negative regulator of pseudo-hyphal growth. We show t hat Cdc11, one of the septins, is delocalised in the mutant, indicating tha t septin localisation is partly controlled by Elm1. Moreover, we show that cytokinesis is delayed in an elm1 Delta mutant. Elm1 levels peak at the end of the cell cycle and Elm1 is localised at the bud neck in a septin-depend ent fashion from bud emergence until the completion of anaphase, at about t he time of cell division. Genetic and biochemical evidence suggest that Elm 1 and the three other septin-localised protein kinases, Hsl1, Gin4 and Kcc4 , work in parallel pathways to regulate septin behaviour and cytokinesis. I n addition, the elm1 Delta morphological defects can be suppressed by delet ion of the SWE1 gene, but not the cytokinesis defect nor the septin misloca lisation, Our results indicate that cytokinesis in budding yeast is regulat ed by Elm1.