title: Plk1-dependent phosphorylation regulates functions of DNA topoisomerase IIalpha in cell cycle progression.
abstract: Plk1 (Polo-like kinase 1) has been documented as a critical regulator of many mitotic events. However, increasing evidence supports the notion that Plk1 might also have functions outside of mitosis. Using biochemical fractionation and RNA interference approaches, we found that Plk1 was required for both G(1)/S and G(2)/M phases and that DNA topoisomerase IIalpha (topoIIalpha) was a potential target for Plk1 in both interphase and mitosis. Plk1 phosphorylates Ser(1337) and Ser(1524) of topoIIalpha. Overexpression of an unphosphorylatable topoIIalpha mutant led to S phase arrest, suggesting that Plk1-associated phosphorylation first occurs in S phase. Moreover, overexpression of the unphosphorylatable topoIIalpha mutant activated the ATM/R-dependent DNA damage checkpoint, probably due to reduced catalytic activity of topoIIalpha, and resulted in accumulation of catenated DNA. Finally, we showed that wild type topoIIalpha, but not the unphosphorylatable mutant, was able to rescue topoIIalpha depletion-induced defects in sister chromatid segregation, indicating that Plk1-associated phosphorylation is essential for the functions of topoIIalpha in mitosis.
authors.affiliation: Department of Biochemistry and the Cancer Center, Purdue University, 175 S. University Street, West Lafayette, IN 47907, USA.
authors.forename: Hongchang
authors.initials: H
authors.lastname: Li
authors.forename: Yun
authors.initials: Y
authors.lastname: Wang
authors.forename: Xiaoqi
authors.initials: X
authors.lastname: Liu
mesh_terms: D019943:Amino Acid Substitution; D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism*; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002842:Chromatids / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage / Q000502:physiology; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D043864:DNA, Catenated / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism; D000097869:Polo-Like Kinase 1
chemical_list: D000951:Antigens, Neoplasm; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins; D004250:DNA Topoisomerases, Type II; D043864:DNA, Catenated; D004268:DNA-Binding Proteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; D000097869:Polo-Like Kinase 1; C576324:ATM protein, human