title: Proto-oncogene FBI-1 represses transcription of p21CIP1 by inhibition of transcription activation by p53 and Sp1.
abstract: Aberrant transcriptional repression through chromatin remodeling and histone deacetylation has been postulated as the driving force for tumorigenesis. FBI-1 (formerly called Pokemon) is a member of the POK family of transcriptional repressors. Recently, FBI-1 was characterized as a critical oncogenic factor that specifically represses transcription of the tumor suppressor gene ARF, potentially leading indirectly to p53 inactivation. Our investigations on transcriptional repression of the p53 pathway revealed that FBI-1 represses transcription of ARF, Hdm2 (human analogue of mouse double minute oncogene), and p21CIP1 (hereafter indicated as p21) but not of p53. FBI-1 showed a more potent repressive effect on p21 than on p53. Our data suggested that FBI-1 is a master controller of the ARF-Hdm2-p53-p21 pathway, ultimately impinging on cell cycle arrest factor p21, by inhibiting upstream regulators at the transcriptional and protein levels. FBI-1 acted as a competitive transcriptional repressor of p53 and Sp1 and was shown to bind the proximal Sp1-3 GC-box and the distal p53-responsive elements of p21. Repression involved direct binding competition of FBI-1 with Sp1 and p53. FBI-1 also interacted with corepressors, such as mSin3A, NCoR, and SMRT, thereby deacetylating Ac-H3 and Ac-H4 histones at the promoter. FBI-1 caused cellular transformation, promoted cell cycle proliferation, and significantly increased the number of cells in S phase. FBI-1 is aberrantly overexpressed in many human solid tumors, particularly in adenocarcinomas and squamous carcinomas. The role of FBI-1 as a master controller of the p53 pathway therefore makes it an attractive therapeutic target.
authors.affiliation: Department of Biochemistry and Molecular Biology, BK21 Project, and Institute for Cancer Research, Yonsei University School of Medicine, Seoul, Korea.
authors.forename: Won-Il
authors.initials: WI
authors.lastname: Choi
authors.forename: Bu-Nam
authors.initials: BN
authors.lastname: Jeon
authors.forename: Chae-Ok
authors.initials: CO
authors.lastname: Yun
authors.forename: Pyung-Hwan
authors.initials: PH
authors.lastname: Kim
authors.forename: Sung-Eun
authors.initials: SE
authors.lastname: Kim
authors.forename: Kang-Yell
authors.initials: KY
authors.lastname: Choi
authors.forename: Se Hoon
authors.initials: SH
authors.lastname: Kim
authors.forename: Man-Wook
authors.initials: MW
authors.lastname: Hur
mesh_terms: D015153:Blotting, Western; D001859:Bone Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002453:Cell Cycle; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D003114:Colony-Forming Units Assay; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D024202:Electrophoretic Mobility Shift Assay; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D016297:Mutagenesis, Site-Directed; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic; D000090063:Proto-Oncogene Mas; D034741:RNA, Small Interfering / Q000494:pharmacology; D016329:Sp1 Transcription Factor / Q000235:genetics*; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic / Q000187:drug effects*; D015533:Transcriptional Activation / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D034741:RNA, Small Interfering; D016329:Sp1 Transcription Factor; C495901:TP53 protein, human; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; C485514:ZBTB7A protein, human