title: p27Kip1 represses transcription by direct interaction with p130/E2F4 at the promoters of target genes.
abstract: The cyclin-cdk (cyclin-dependent kinase) inhibitor p27Kip1 (p27) has a crucial negative role on cell cycle progression. In addition to its classical role as a cyclin-cdk inhibitor, it also performs cyclin-cdk-independent functions as the regulation of cytoskeleton rearrangements and cell motility. p27 deficiency has been associated with tumor aggressiveness and poor clinical outcome, although the mechanisms underlying this participation still remain elusive. We report here a new cellular function of p27 as a transcriptional regulator in association with p130/E2F4 complexes that could be relevant for tumorigenesis. We observed that p27 associates with specific promoters of genes involved in important cellular functions as processing and splicing of RNA, mitochondrial organization and respiration, translation and cell cycle. On these promoters p27 co-localizes with p130, E2F4 and co-repressors as histone deacetylases (HDACs) and mSIN3A. p27 co-immunoprecipitates with these proteins and by affinity chromatography, we demonstrated a direct interaction of p27 with p130 and E2F4 through its carboxyl-half. We have also shown that p130 recruits p27 on the promoters, and there p27 is needed for the subsequent recruitment of HDACs and mSIN3A. Expression microarrays and luciferase assays revealed that p27 behaves as transcriptional repressor of these p27-target genes (p27-TGs). Finally, in human tumors, we established a correlation with overexpression of p27-TGs and poor survival. Thus, this new function of p27 as a transcriptional repressor could have a role in the major aggressiveness of tumors with low levels of p27.
authors.affiliation: Department of Cell Biology, Immunology and Neurosciences, University of Barcelona, IDIBAPS, and Institut Municipal d' Investigacions Mèdiques-Hospital del Mar, Barcelona, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Pippa
authors.forename: L
authors.initials: L
authors.lastname: Espinosa
authors.forename: G
authors.initials: G
authors.lastname: Gundem
authors.forename: R
authors.initials: R
authors.lastname: García-Escudero
authors.forename: A
authors.initials: A
authors.lastname: Dominguez
authors.forename: S
authors.initials: S
authors.lastname: Orlando
authors.forename: E
authors.initials: E
authors.lastname: Gallastegui
authors.forename: C
authors.initials: C
authors.lastname: Saiz
authors.forename: A
authors.initials: A
authors.lastname: Besson
authors.forename: M J
authors.initials: MJ
authors.lastname: Pujol
authors.forename: N
authors.initials: N
authors.lastname: López-Bigas
authors.forename: J M
authors.initials: JM
authors.lastname: Paramio
authors.forename: A
authors.initials: A
authors.lastname: Bigas
authors.forename: O
authors.initials: O
authors.lastname: Bachs
mesh_terms: D000818:Animals; D056970:Co-Repressor Proteins / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism*; D050704:E2F4 Transcription Factor / Q000378:metabolism*; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D008954:Models, Biological; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism / Q000401:mortality; D011379:Prognosis; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D050717:Retinoblastoma-Like Protein p130 / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D056970:Co-Repressor Proteins; D050704:E2F4 Transcription Factor; D050717:Retinoblastoma-Like Protein p130; D050760:Cyclin-Dependent Kinase Inhibitor p27