Identification of both Myt-1 and Wee-1 as necessary mediators of the p21-independent inactivation of the cdc-2/cyclin B1 complex and growth inhibition of TRAMP cancer cells by genistein.
BACKGROUND
The G2/M cell-cycle arrest is one mechanism by which genistein exerts its anti-proliferative effects, and the proposed underlying causes encompass the transcriptional repression of cyclin B1 and the activation of p21. However, the involvement of upstream kinases Myt-1 and Wee-1 in this arrest remains to be elucidated.


METHODS
Myt-1 and Wee-1 modulation by genistein was examined via Western blot analysis and the effect of their inhibition by siRNA on cyclin B1 levels/localization, cdc2 kinase activity, and cellular proliferation of genistein-treated TRAMP-C2 cells was determined.


RESULTS
The sustained G2/M arrest by genistein in TRAMP-C2 cells is associated with increased phospho-cdc2(Tyr15), decreased cdc2 protein, and cytoplasmic retention of cyclinB1, resulting in decreased cdc2 kinase activity independently of p21. Genistein treatment increased Myt-1 levels and decreased Wee-1 phosphorylation. Downregulation of Myt-1 and Wee-1 by siRNA restored cdc2 levels, its kinase activity, cyclinB1 nuclear localization, and partially restored cell proliferation of genistein-treated cells.


CONCLUSIONS
Myt-1 and Wee-1 rather than p21 are necessary for genistein-induced G2/M arrest in TRAMP-C2 cells and their inhibition partially restores proliferation of TRAMP-C2 cells in the presence of genistein.
Touny
Lara H El
LH
Department of Biochemistry, Molecular and Cellular Biology, Georgetown University Medical Center, Washington, District of Columbia 20057, USA.
Banerjee
Partha P
PP
D000230:Adenocarcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D064127:Aurora Kinases; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D016195:G2 Phase / Q000187:drug effects; D019833:Genistein / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D016588:Anticarcinogenic Agents; C534700:Ccnb1 protein, mouse; D018797:Cell Cycle Proteins; D019926:Cyclin B; D056744:Cyclin B1; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; C489726:Myt1 protein, mouse; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D014157:Transcription Factors; D019833:Genistein; D011505:Protein-Tyrosine Kinases; C499348:Wee1 protein, mouse; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase