title: Modulation of p300/CBP Acetylation of Nucleosomes by Bromodomain Ligand I-CBP112.
abstract: The histone acetyltransferase (HAT) enzymes p300 and CBP are closely related paralogs that serve as transcriptional coactivators and have been found to be dysregulated in cancer and other diseases. p300/CBP is a multidomain protein and possesses a highly conserved bromodomain that has been shown to bind acetylated Lys residues in both proteins and various small molecules, including I-CBP112 and CBP30. Here we show that the ligand I-CBP112 can stimulate nucleosome acetylation up to 3-fold while CBP30 does not. Activation of p300/CBP by I-CBP112 is not observed with the isolated histone H3 substrate but requires a nucleosome substrate. I-CBP112 does not impact nucleosome acetylation by the isolated p300 HAT domain, and the effects of I-CBP112 on p300/CBP can be neutralized by CBP30, suggesting that I-CBP112 likely allosterically activates p300/CBP through bromodomain interactions. Using mass spectrometry and Western blots, we have found that I-CBP112 particularly stimulates acetylation of Lys18 of histone H3 (H3K18) in nucleosomes, an established in vivo site of p300/CBP. In addition, we show that I-CBP112 enhances H3K18 acetylation in acute leukemia and prostate cancer cells in a concentration range commensurate with its antiproliferative effects. Our findings extend the known pharmacology of bromodomain ligands in the regulation of p300/CBP and suggest a novel approach to modulating histone acetylation in cancer.
authors.affiliation: Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine , Baltimore, Maryland 21205, United States.
authors.forename: Beth E
authors.initials: BE
authors.lastname: Zucconi
authors.affiliation: Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine , Baltimore, Maryland 21205, United States.
authors.forename: Birgit
authors.initials: B
authors.lastname: Luef
authors.affiliation: Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine , Baltimore, Maryland 21205, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.affiliation: Department of Cancer Biology, Fox Chase Cancer Center , Philadelphia, Pennsylvania 19111, United States.
authors.forename: Ryan A
authors.initials: RA
authors.lastname: Henry
authors.affiliation: Department of Biophysics, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Ilana M
authors.initials: IM
authors.lastname: Nodelman
authors.affiliation: Department of Biophysics, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Bowman
authors.affiliation: Department of Cancer Biology, Fox Chase Cancer Center , Philadelphia, Pennsylvania 19111, United States.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Andrews
authors.affiliation: Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine , Baltimore, Maryland 21205, United States.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Cole
mesh_terms: D000107:Acetylation; D017605:Bromine Compounds / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects; D018360:Crystallography, X-Ray; D050881:E1A-Associated p300 Protein / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006801:Humans; D007938:Leukemia / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009707:Nucleosomes / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D011485:Protein Binding; D011487:Protein Conformation; D014407:Tumor Cells, Cultured; D050880:p300-CBP Transcription Factors / Q000378:metabolism*
chemical_list: D017605:Bromine Compounds; D006657:Histones; D009707:Nucleosomes; D050881:E1A-Associated p300 Protein; C494360:EP300 protein, human; D050880:p300-CBP Transcription Factors