Cell cycle regulation of human WEE1.

Abstract

Corresponding authorCommunicated by P.Nurse WEE1 kinase negatively regulates entry into mitosis by catalyzing the inhibitory tyrosine phosphorylation of CDC2Icyclin B kinase. We report here an investigation of human WEEL. Endogenous WEE1 migrates as an -94 kDa protein in SDS-PAGE, substantially larger than the 49 kDa protein encoded by the original human WEE] cDNA clone that was truncated at the 5'-end. Antibody depletion experiments demonstrate that WEE1 accounts for most of the activity that phosphorylates CDC2 on Tyrl5 in an in vitro assay of HeLa cell lysates, hence it is likely to have an important role in the mitotic control of human cells. WEE1 activity was not found to be elevated in HeLa cells arrested in S phase, suggesting that unreplicated DNA does not delay M phase by hyperactivating WEEL. WEE1 activity is strongly suppressed during M phase, suggesting that negative regulation of WEE1 could be part of the mechanism by which activation of CDC2/ cyclin B kinase is promoted during the G2/M transition. M phase WEE1 is re-activated in samples prepared in the absence of protein phosphatase inhibitors, demonstrating that WEE1 is inhibited by a mechanism that requires protein phosphorylation.

Changes in Regulatory Phosphorylation of Cdc25C Ser287 and Wee1 Ser549 during Normal Cell Cycle Progression and Checkpoint Arrests

“…In mammalian somatic cells, the fate of wee1 is less clear: some studies found that wee1 protein was reduced during mitosis (Baldin and Ducommun, 1995;Watanabe et al, 1995), whereas others found that it was stable (McGowan and Russell, 1995;Parker et al, 1995). In Xenopus egg extracts, immunoblots of endogenous wee1 show that overall wee1 protein levels are essentially constant across the early embryonic cell cycles (Walter et al, 1997), a point that we confirm here.…”

Knockdown of Chk1, Wee1 and Myt1 by RNA Interference Abrogates G2 Checkpoint and Induces Apoptosis

“…8 The inhibitory phosphorylations of threonine 14 (T14) and tyrosine 15 (Y15) at the ATP-binding pocket are mediated by Wee1 and Myt1 kinases. [9][10][11][12][13] Wee1 is the major kinase phosphorylating the Y15 site. While Myt1 preferentially phosphorylates the T14 site, it can also phosphorylate the Y15 site.…”

A rate limiting function of cdc25A for S phase entry inversely correlates with tyrosine dephosphorylation of Cdk2

“…These inhibitory phosphorylations result from the action of the wee1/mik1 family of kinases (Lundgren et al, 1991;Atherton-Fessler et al, 1993;McGowan and Russell, 1995) and are reversed by cdc25 phosphatases (Gautier et al, 1991;Draetta and Eckstein, 1997). Three cdc25 phosphatases have been identi®ed in mammals, and the di erent isoforms, designated A, B, and C, share 40 ± 50% amino acid identity (Sandhu et al, 1990;Nagata et al, 1991;Galaktionov and Beach, 1991).…”