Multiple splicing variants of cdc25B regulate G2/M progression

Progression through G2 phase into mitosis is regulated by the activation of the mitotic cyclin/cdk complexes, which are in turn activated cdc25B and cdc25C phosphatases. Here we report that alternate splicing produces at least five variants of cdc25B, although only cdc25B2 and cdc25B3 are detectable as proteins. Analysis of these two variants shows that cdc25B2 is expressed at lower levels relative to cdc25B3 in all cell lines tested, and the expression of both increased markedly during G2 and mitosis. Overexpression of the catalytically inactive version of either cdc25B variant produced a G2 arrest implicating both in regulating G2/M progression. (C) 1999 Academic Press.