Hsp 90 interaction with Cdc2 and Plo1 kinases contributes to actomyosin ring condensation in fission yeast

Abstract

In Schizosaccharomyces pombe, cytokinesis occurs by ordered recruitment of actomyosin components at the division site, followed by lateral condensation to produce a ring-like structure early in anaphase, which eventually matures and contracts at the end of mitosis. We found that in temperature-sensitive hsp 90-w1 mutant cells, encoding an Hsp 90 mutant protein, ring components were recruited to form a cortical network at the division site, but this network failed to condense into a compact ring, suggesting a role for Hsp 90 in this particular step. hsp 90-w1 mutant shows strong genetic interaction with specific mutant alleles of the fission yeast cdc2, such as cdc2-33. Interestingly, actomyosin ring defects in hsp 90-w1 cdc2-33 mutant cells resembled that of hsp 90-w1 single mutant at restrictive temperature. Noteworthy, similar genetic interaction was found with a mutant allele of polo-like kinase, plo1-ts4, suggesting that Hsp 90 collaborates with Cdc2 and Plo1 cell cycle kinases to condense medial ring components. In vitro analyses suggested that Cdc2 and Plo1 physically interact with Hsp 90. Association of Cdc2 to Hsp 90 was ATP independent, while Plo1 binds to this chaperone in an ATP-dependent manner, indicating that these two kinases interact with different Hsp 90 complexes. Overall, our analyses of hsp 90-w1 reveal a possible role for this chaperone in medial ring condensation in association with Cdc2 and Plo1 kinases.