title: B56 regulatory subunit of protein phosphatase 2A mediates valproic acid-induced p300 degradation.
abstract: Transcriptional coactivator p300 is required for embryonic development and cell proliferation. Valproic acid, a histone deacetylase inhibitor, is widely used in the therapy of epilepsy and bipolar disorder. However, it has intrinsic teratogenic activity through unidentified mechanisms. We report that valproic acid stimulates proteasome-dependent p300 degradation through augmentation of gene expression of the B56gamma regulatory subunits of protein phosphatase 2A. The B56gamma3 regulatory and catalytic subunits of protein phosphatase 2A interact with p300. Overexpression of the B56gamma3 subunit leads to proteasome-mediated p300 degradation and represses p300-dependent transcriptional activation, which requires the B56gamma3 interaction domain of p300. Conversely, silencing of the B56gamma subunit expression by RNA interference increases the stability and transcriptional activity of the coactivator. Our study establishes the functional interaction between protein phosphatase 2A and p300 activity and provides direct evidence for signal-dependent control of p300 function.
authors.affiliation: Ottawa Health Research Institute, 725 Parkdale Ave., Ottawa, Ontario, Canada K1Y 4E9.
authors.forename: Jihong
authors.initials: J
authors.lastname: Chen
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: St-Germain
authors.forename: Qiao
authors.initials: Q
authors.lastname: Li
mesh_terms: D004791:Enzyme Inhibitors / Q000378:metabolism*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D019319:Okadaic Acid / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D054648:Protein Phosphatase 2; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014635:Valproic Acid / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D021122:Protein Subunits; D034741:RNA, Small Interfering; D015534:Trans-Activators; D019319:Okadaic Acid; D014635:Valproic Acid; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease