title: Altered histone monoubiquitylation mediated by mutant huntingtin induces transcriptional dysregulation.
abstract: Although transcriptional dysregulation is a critical pathogenic mechanism in Huntington's disease (HD), it is still not known how mutant huntingtin causes it. Here we show that alteration of histone monoubiquitylation is a key mechanism. Disrupted interaction of huntingtin with Bmi-1, a component of the hPRC1L E3 ubiquitin ligase complex, increases monoubiquityl histone H2A (uH2A) levels in a cell culture model of HD. Genes with expression that is repressed in transgenic R6/2 mouse brain have increased uH2A and decreased uH2B at their promoters, whereas actively transcribed genes show the opposite pattern. Reduction in uH2A reverses transcriptional repression and inhibits methylation of histone H3 at lysine 9 in cell culture. In contrast, reduction in uH2B induces transcriptional repression and inhibits methylation of histone H3 at lysine 4. This is the first report to demonstrate hPRC1L as a huntingtin-interacting histone modifying complex and a crucial role for histone monoubiquitylation in mammalian brain gene expression, which broadens our understanding of histone code. These findings also provide a rationale for targeting histone monoubiquitylation for therapy in HD.
authors.affiliation: MassGeneral Institute for Neurodegenerative Disease, Department of Neurology, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
authors.forename: Mee-Ohk
authors.initials: MO
authors.lastname: Kim
authors.forename: Prianka
authors.initials: P
authors.lastname: Chawla
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Overland
authors.forename: Eva
authors.initials: E
authors.lastname: Xia
authors.forename: Ghazaleh
authors.initials: G
authors.lastname: Sadri-Vakili
authors.forename: Jang-Ho J
authors.initials: JH
authors.lastname: Cha
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002478:Cells, Cultured; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics / Q000378:metabolism; D008745:Methylation; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D063150:Polycomb Repressive Complex 1; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D014158:Transcription, Genetic; D054875:Ubiquitination
chemical_list: C069077:BMI1 protein, human; C086055:HTT protein, human; D006657:Histones; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D063150:Polycomb Repressive Complex 1