title: The proto-oncoprotein KR-POK represses transcriptional activation of CDKN1A by MIZ-1 through competitive binding.
abstract: The BTB/POZ family of proteins has been implicated in multiple biological processes, including tumourigenesis, DNA damage responses and cell cycle progression and development. MIZ-1 (Myc-interacting zinc-finger protein 1) is known to activate transcription of CDKN1A. We recently found that a kidney cancer-related POK transcription factor, KR-POK, is highly expressed in kidney, brain and bone marrow cancer tissues and is a potential proto-oncoprotein. Mouse Kr-pok represses transcription of the CDKN1A by acting on the proximal promoter. The BiFC/FRET assay, co-immunoprecipitation and glutathione S-transferase-fusion protein pull-down assay indicate that MIZ-1 and Kr-pok interact via their POZ domains. Oligoucleotide pull-down assays and chromatin immunoprecipitation assays revealed that MIZ-1 binds to the proximal GC-box#3 (bp, -55 to -63) and the MIZ-1-binding elements, MRE-A (bp, -90 to -64) and MRE-B (bp, -27 to -17). Interestingly, MIZ-1 also binds to the distal p53-binding elements. Kr-pok binds to the proximal GC-box#1 (bp, -95 to -100) and #3 (bp, -55 to -63) relatively strongly. It also shows weak binding to the MREs and the distal p53-binding elements. Kr-pok competes with MIZ-1 in binding to these elements and represses transcription by inhibiting MIZ-1/p300 recruitment, which decreases the acetylation of histones H3 and H4. Our data indicate that Kr-pok stimulates cell proliferation by interfering with the function of MIZ-1 in CDKN1A gene transcription using a mechanism that is radically different from other MIZ-1-interacting proteins, such as B-cell lymphoma 6, c-Myc and Gfi-1.
authors.affiliation: Department of Biochemistry and Molecular Biology, Yonsei University School of Medicine, Seoul, Korea.
authors.forename: K M
authors.initials: KM
authors.lastname: Lee
authors.forename: W I
authors.initials: WI
authors.lastname: Choi
authors.forename: D I
authors.initials: DI
authors.lastname: Koh
authors.forename: Y J
authors.initials: YJ
authors.lastname: Kim
authors.forename: B N
authors.initials: BN
authors.lastname: Jeon
authors.forename: J H
authors.initials: JH
authors.lastname: Yoon
authors.forename: C E
authors.initials: CE
authors.lastname: Lee
authors.forename: S H
authors.initials: SH
authors.lastname: Kim
authors.forename: J
authors.initials: J
authors.lastname: Oh
authors.forename: M W
authors.initials: MW
authors.lastname: Hur
mesh_terms: D001667:Binding, Competitive; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism*; D016393:Lymphoma, B-Cell / Q000235:genetics; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000502:physiology*; D015533:Transcriptional Activation
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D047908:Intracellular Signaling Peptides and Proteins; D051741:Kruppel-Like Transcription Factors; D011506:Proteins; C107961:ZBTB17 protein, human; C110461:ZBTB7C protein, human