title: Individual Bromodomains of Polybromo-1 Contribute to Chromatin Association and Tumor Suppression in Clear Cell Renal Carcinoma.
abstract: The architecture of chromatin is governed, in part, by ATP-dependent chromatin remodelers. These multiprotein complexes contain targeting domains that recognize post-translational marks on histones. One such targeting domain is the bromodomain (BD), which recognizes acetyl-lysines and recruits proteins to sites of acetylation across the genome. Polybromo1 (PBRM1), a subunit of the Polybromo-associated BRG1- or hBRM-associated factors (PBAF) chromatin remodeler, contains six tandem BDs and is frequently mutated in clear cell renal cell carcinoma (ccRCC). Mutations in thePBRM1gene often lead to the loss of protein expression; however, missense mutations inPBRM1have been identified and tend to cluster in the BDs, particularly BD2 and BD4, suggesting that individual BDs are critical for PBRM1 function. To study the role of these six BDs, we inactivated each of the six BDs of PBRM1 and re-expressed these mutants in Caki2 cells (ccRCC cells with the loss of function mutation inPBRM1). Four of the six BDs abrogated PBRM1 tumor suppressor function, gene regulation, and chromatin affinity with the degree of importance correlating strongly to the rate of missense mutations in patients. Furthermore, we identified BD2 as the most critical for PBRM1 and confirmed BD2-mediated association to histone H3 peptides acetylated at lysine 14 (H3K14Ac), validating the importance of this specific acetylation mark for PBRM1 binding. From these data, we conclude that four of the BDs act together to target PBRM1 to sites on chromatin; when a single BD is mutated, PBRM1 no longer controls gene expression properly, leading to increased cell proliferation.
authors.affiliation: From the Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907.
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Porter
authors.affiliation: From the Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907 edykhui@purdue.edu.
authors.forename: Emily C
authors.initials: EC
authors.lastname: Dykhuizen
mesh_terms: D002460:Cell Line; D049109:Cell Proliferation; D002843:Chromatin / Q000378:metabolism*; D004268:DNA-Binding Proteins; D015870:Gene Expression; D006801:Humans; D007680:Kidney Neoplasms / Q000378:metabolism / Q000473:pathology*; D020125:Mutation, Missense; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009857:Oncogenes; D011485:Protein Binding; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C102195:PBRM1 protein, human; D014157:Transcription Factors
keywords: Polybromo-1; acetylation; bromodomain; bromodomains; cancer; cell growth; chromatin remodeling; epigenetics; histone acetylation; renal cancer