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Biochem Biophys Res Commun. 2003 Jan 3;300(1):135-40.

Dimerization of the Polycomb-group protein Mel-18 is regulated by PKC phosphorylation.

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Department of Immunology, Graduate School of Science, Hiroshima University, 1-2-3, Kasumi, Minami-ku, Japan.


The Polycomb-group (Pc-G) gene products form complexes via protein-protein interactions and maintain the transcriptional repression of genes involved in embryogenesis, cell cycle, and tumorigenesis. Previously, we have shown that mouse Mel-18, a Pc-G protein, has tumor suppressor gene-like activity and negatively regulates transcription. Here, we show in vitro by pull-down assays and in vivo in transiently transfected COS-7 cells that Mel-18 forms homodimers. Deletion analysis revealed that the N-terminal RING-finger and alpha-helix domains are required for homodimer formation. In addition, we demonstrated that Mel-18 homo-dimerization is regulated by protein kinase C (PKC) and protein phosphatases, such that dephosphorylated Mel-18 is able to homo-dimerize. These results suggest that the stoichiometry and/or equilibrium of subunits of the class II Polycomb complex containing Mel-18 might be regulated by changes in phosphorylation status via the PKC signaling pathway.

[Indexed for MEDLINE]

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