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Title

Sid2 phosphoregulation of anillin-related Mid1 nuclear localization and fission yeast cytokinesis

Department

Cell and Molecular Biology

College

College of Liberal Arts and Sciences

Disciplines

Life Sciences

Abstract

Cortical nodes assemble during interphase and serve as the foundation to generate a contractile ring for fission yeast cytokinesis. The anillin-related protein Mid1 serves as a central organizer of cytokinesis by anchoring cortical nodes to the cell membrane and recruiting proteins that incorporate into the contractile ring. Interestingly, Mid1 dissociates from the cell cortex prior to contractile ring constriction. However, it remains unclear if Mid1 departure influences ring function. Given that localization of Mid1 to the cell cortex is phosphorylation dependent, we hypothesized that Mid1 departure from the cell cortex may be similarly controlled. Indeed we find that Sid2 kinase directly phosphorylates Mid1. Phosphosite mapping and phenotypic analyses of phosphosite mutants reveal defects in Mid1 nuclear accumulation following septation and during interphase. Instead, Mid1 remains concentrated in the cytoplasm and appears to localize as cortical nodes. Strikingly, a reproducible percentage of phosphosite mutants display two contractile rings and/or disorganized contractile rings. To further examine Mid1 localization, we combined the Mid1 phosphosite mutant with a temperature-sensitive mutation that arrests cells at anaphase when Mid1 should be concentrated in the nucleus. In the phosphosite mutant, Mid1 fails to move from the cytoplasm to the nucleus. Instead Mid1 accumulates in punctate clusters or remains in rings that are often abnormal. We conclude that Sid2 phosphoregulation of Mid1 nuclear accumulation during interphase promotes proper contractile ring function in mitosis. This research is supported by National Science Foundation RUI Award #1157997.

Conference Name

American Society of Cell Biology Annual Meeting

Conference Location

Philadelphia, PA

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