title: Dissecting the M phase-specific phosphorylation of serine-proline or threonine-proline motifs.
abstract: M phase induction in eukaryotic cell cycles is associated with a burst of protein phosphorylation, primarily at serine or threonine followed by proline (S/TP motif). The mitotic phosphoprotein antibody MPM-2 recognizes a significant subset of mitotically phosphorylated S/TP motifs; however, the required surrounding sequences of and the key kinases that phosphorylate these S/TP motifs remain to be determined. By mapping the mitotic MPM-2 epitopes in Xenopus Cdc25C and characterizing the mitotic MPM-2 epitope kinases in Xenopus oocytes and egg extracts, we have determined that phosphorylation of TP motifs that are surrounded by hydrophobic residues at both -1 and +1 positions plays a dominant role in M phase-associated burst of MPM-2 reactivity. Although mitotic Cdk and MAPK may phosphorylate subsets of these motifs that have a basic residue at the +2 position and a proline residue at the -2 position, respectively, the majority of these motifs that are preferentially phosphorylated in mitosis do not have these features. The M phase-associated burst of MPM-2 reactivity can be induced in Xenopus oocytes and egg extracts in the absence of MAPK or Cdc2 activity. These findings indicate that the M phase-associated burst of MPM-2 reactivity represents a novel type of protein phosphorylation in mitotic regulation.
authors.affiliation: Department of Experimental Therapeutics, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Chuan Fen
authors.initials: CF
authors.lastname: Wu
authors.forename: Ruoning
authors.initials: R
authors.lastname: Wang
authors.forename: Qianjin
authors.initials: Q
authors.lastname: Liang
authors.forename: Jianjiao
authors.initials: J
authors.lastname: Liang
authors.forename: Wenke
authors.initials: W
authors.lastname: Li
authors.forename: Sung Yun
authors.initials: SY
authors.lastname: Jung
authors.forename: Jun
authors.initials: J
authors.lastname: Qin
authors.forename: Sue-Hwa
authors.initials: SH
authors.lastname: Lin
authors.forename: Jian
authors.initials: J
authors.lastname: Kuang
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics / Q000276:immunology; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001665:Binding Sites / Q000235:genetics; D000939:Epitopes / Q000276:immunology / Q000378:metabolism; D005260:Female; D015151:Immunoblotting; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D008938:Mitosis; D009865:Oocytes / Q000378:metabolism; D010766:Phosphorylation; D011392:Proline / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D013912:Threonine / Q000235:genetics / Q000378:metabolism*; D014981:Xenopus; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D020687:cdc25 Phosphatases / Q000235:genetics / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D011993:Recombinant Fusion Proteins; D029867:Xenopus Proteins; D013912:Threonine; D012694:Serine; D011392:Proline; D020928:Mitogen-Activated Protein Kinases; D020687:cdc25 Phosphatases