title: Functional characterization of human Polycomb-like 3 isoforms identifies them as components of distinct EZH2 protein complexes.
abstract: PcG (Polycomb group) proteins are conserved transcriptional repressors essential to regulate cell fate and to maintain epigenetic cellular memory. They work in concert through two main families of chromatin-modifying complexes, PRC1 (Polycomb repressive complex 1) and PRC2-4. In Drosophila, PRC2 contains the H3K27 histone methyltransferase E(Z) whose trimethylation activity towards PcG target genes is stimulated by PCL (Polycomb-like). In the present study, we have examined hPCL3, one of its three human paralogues. Through alternative splicing, hPCL3 encodes a long isoform, hPCL3L, containing an N-terminal TUDOR domain and two PHDs (plant homeodomains) and a smaller isoform, hPCL3S, lacking the second PHD finger (PHD2). By quantitative reverse transcription-PCR analyses, we showed that both isoforms are widely co-expressed at high levels in medulloblastoma. By co-immunoprecipitation analyses, we demonstrated that both isoforms interact with EZH2 through their common TUDOR domain. However, the hPCL3L-specific PHD2 domain, which is better conserved than PHD1 in the PCL family, is also involved in this interaction and implicated in the self-association of hPCL3L. Finally, we have demonstrated that both hPCL3 isoforms are physically associated with EZH2, but in different complexes. Our results provide the first evidence that the two hPCL3 isoforms belong to different complexes and raise important questions about their relative functions, particularly in tumorigenesis.
authors.affiliation: CNRS UMR 8161, Institut de Biologie de Lille, Université Lille Nord de France, IFR 142, 1 Rue Calmette, 59017 Lille Cedex, France.
authors.forename: Gaylor
authors.initials: G
authors.lastname: Boulay
authors.forename: Claire
authors.initials: C
authors.lastname: Rosnoblet
authors.forename: Cateline
authors.initials: C
authors.lastname: Guérardel
authors.forename: Pierre-Olivier
authors.initials: PO
authors.lastname: Angrand
authors.forename: Dominique
authors.initials: D
authors.lastname: Leprince
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D000071221:Enhancer of Zeste Homolog 2 Protein; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D047468:Immunoprecipitation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D063151:Polycomb Repressive Complex 2; D011393:Procollagen-Proline Dioxygenase / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D009687:Nuclear Proteins; C497703:PHF19 protein, human; D020033:Protein Isoforms; D014157:Transcription Factors; C490190:EGLN1 protein, human; D011393:Procollagen-Proline Dioxygenase; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D011495:Histone-Lysine N-Methyltransferase; C524066:PRC2 protein, Drosophila; D063151:Polycomb Repressive Complex 2