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Updated: Jun 15, 2026
Identification of Post-translational Modifications of Plant Protein Complexes
Published on: February 22, 2014
Dissecting the M phase-specific phosphorylation of serine-proline or threonine-proline motifs
Chuan Fen Wu1, Ruoning Wang, Qianjin Liang
1Department of Experimental Therapeutics, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
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.
Insights
Mitotic protein phosphorylation, recognized by the MPM-2 antibody, is driven by TP motifs flanked by hydrophobic residues. This novel phosphorylation event occurs independently of MAPK or Cdc2 activity during M phase.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Eukaryotic M phase involves a surge in protein phosphorylation, particularly at serine/threonine followed by proline (S/TP) motifs.
- The MPM-2 antibody targets a subset of these mitotic S/TP phosphorylation sites, but the specific kinase targets and sequence requirements are not fully understood.
Purpose of the Study:
- To identify the key kinases and surrounding sequences responsible for M phase-associated phosphorylation recognized by the MPM-2 antibody.
- To characterize the dominant phosphorylation events driving MPM-2 reactivity during mitosis.
Main Methods:
- Mapping of mitotic MPM-2 epitopes within Xenopus Cdc25C.
- Characterization of MPM-2 epitope kinases in Xenopus oocytes and egg extracts.
Main Results:
- Phosphorylation of TP motifs flanked by hydrophobic residues at the -1 and +1 positions is crucial for MPM-2 reactivity during M phase.
- Mitotic Cdk and MAPK phosphorylate specific subsets of these motifs, but the majority of MPM-2 reactive sites lack these features.
- The M phase-associated MPM-2 reactivity can be induced independently of MAPK or Cdc2 activity.
Conclusions:
- A novel type of protein phosphorylation contributes to mitotic regulation, characterized by TP motifs with flanking hydrophobic residues.
- This phosphorylation event, recognized by MPM-2, is a significant feature of the M phase-associated phosphorylation burst.
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