title: TIP49 regulates beta-catenin-mediated neoplastic transformation and T-cell factor target gene induction via effects on chromatin remodeling.
abstract: Beta-catenin has a key role in Wnt signaling via effects on T-cell factor (TCF)-mediated transcription. Mutational defects in beta-catenin regulation are seen in many cancers, leading to elevated beta-catenin levels, enhanced binding of beta-catenin to TCFs, and increased expression of TCF-regulated genes. Factors cooperating with beta-catenin in transcription of TCF-regulated genes are not well defined. TIP49, an ATPase previously implicated as a cofactor for oncogenic transformation by c-Myc, has been shown to bind to beta-catenin. We found that expression of an ATPase-deficient mutant form of TIP49 (TIP49D302N) substantially inhibited beta-catenin-mediated neoplastic transformation of immortalized rat epithelial cells and anchorage-independent growth of human colon cancer cells with deregulated beta-catenin. The TIP49D302N mutant inhibited beta-catenin-mediated activation of TCF-dependent cellular genes. Similar inhibition of the expression of beta-catenin/TCF-dependent genes was seen with small interfering RNA approaches against endogenous TIP49. TIP49 was found in complexes with chromatin remodeling and histone-modifying factors and cofactors, including the TIP60 histone acetylase-associated proteins transactivation/transformation-domain associated protein (TRRAP) and BAF53. Using chromatin immunoprecipitation methods, the TIP49, TIP60, and TRRAP proteins were found to interact with sequences in the regulatory region of the gene for ITF-2, a TCF-dependent cellular gene. The ability of TIP49D302N to inhibit ITF-2 gene expression was linked to decreased acetylation of histones in the vicinity of the TCF-binding sites in the ITF-2 promoter region. We suggest that TIP49 is an important cofactor in beta-catenin/TCF gene regulation in normal and neoplastic cells, likely functioning in chromatin remodeling.
authors.affiliation: Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Feng
authors.forename: Nana
authors.initials: N
authors.lastname: Lee
authors.forename: Eric R
authors.initials: ER
authors.lastname: Fearon
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000107:Acetylation; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D004265:DNA Helicases / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics; D017930:Genes, Reporter / Q000235:genetics; D045325:HCT116 Cells; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000235:genetics*; D051820:TCF Transcription Factors; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D000073940:Transcription Factor 4; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection; D051176:beta Catenin
chemical_list: C495270:CTNNB1 protein, human; D002352:Carrier Proteins; D002843:Chromatin; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D006657:Histones; D034741:RNA, Small Interfering; D051820:TCF Transcription Factors; C544894:TCF7L2 protein, human; C491192:Tcf4 protein, rat; C553059:Tcf7l2 protein, rat; D015534:Trans-Activators; D000073940:Transcription Factor 4; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; D051176:beta Catenin; D000074183:ATPases Associated with Diverse Cellular Activities; D004265:DNA Helicases; C486549:RUVBL1 protein, human; C122079:RUVBL2 protein, human; C486550:Ruvbl1 protein, rat