A role for Hsp90 in cell cycle control: Wee1 tyrosine kinase activity requires interaction with Hsp90.

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Abstract
Wee1 protein kinase regulates the length of G2 phase by carrying out the inhibitory tyrosyl phosphorylation of Cdc2‐cyclin B kinase. Mutations were isolated that suppressed the G2 cell cycle arrest caused by overproduction of Wee1. One class of swo (suppressor of wee1 overproduction) mutation, exemplified by swo1‐26, also caused a temperature sensitive lethal phenotype in a wee1+ background. The swo1+ gene encodes a member of the Hsp90 family of stress proteins. Swo1 is essential for viability at all temperatures. Swo1 coimmunoprecipitates with Wee1, showing that the two proteins interact. The swo1‐26 mutant undergoes premature mitosis when grown at a semi‐permissive temperature. These data strongly indicate that formation of active Wee1 tyrosine kinase requires interaction with Swo1, perhaps in a manner analogous to the previously demonstrated interaction between Hsp90 and v‐src tyrosine kinase. These observations demonstrate a unexpected role for Hsp90 in cell cycle control.