title: HMBA releases P-TEFb from HEXIM1 and 7SK snRNA via PI3K/Akt and activates HIV transcription.
abstract: Hexamethylene bisacetamide (HMBA) is a potent inducer of cell differentiation and HIV production in chronically infected cells. However, its mechanism of action remains poorly defined. In this study, we demonstrate that HMBA activates transiently the PI3K/Akt pathway, which leads to the phosphorylation of HEXIM1 and the subsequent release of active positive transcription elongation factor b (P-TEFb) from its transcriptionally inactive complex with HEXIM1 and 7SK small nuclear RNA (snRNA). As a result, P-TEFb is recruited to the HIV promoter to stimulate transcription elongation and viral production. Despite the continuous presence of HMBA, the released P-TEFb reassembles rapidly with 7SK snRNA and HEXIM1. In contrast, a mutant HEXIM1 protein that cannot be phosphorylated and released from P-TEFb and 7SK snRNA via the PI3K/Akt pathway antagonizes this HMBA-mediated induction of viral production. Thus, our studies reveal how HIV transcription is induced by HMBA and suggest how modifications in the equilibrium between active and inactive P-TEFb could contribute to cell differentiation.
authors.affiliation: Department of Medicine, Rosalind Russell Medical Research Center, University of California San Francisco, San Francisco, California, USA.
authors.forename: Xavier
authors.initials: X
authors.lastname: Contreras
authors.forename: Matjaz
authors.initials: M
authors.lastname: Barboric
authors.forename: Tina
authors.initials: T
authors.lastname: Lenasi
authors.forename: B Matija
authors.initials: BM
authors.lastname: Peterlin
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D015967:Gene Expression Regulation, Viral / Q000187:drug effects*; D015497:HIV-1 / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D042925:Positive Transcriptional Elongation Factor B / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism*; D014157:Transcription Factors
chemical_list: D000081:Acetamides; D000970:Antineoplastic Agents; D019869:Phosphatidylinositol 3-Kinases; D042925:Positive Transcriptional Elongation Factor B; D051057:Proto-Oncogene Proteins c-akt; D016601:RNA-Binding Proteins; D017411:Ribonucleoproteins, Small Nuclear; D014157:Transcription Factors; C476123:HEXIM1 protein, human; C494918:AKT1 protein, human; C014026:hexamethylene bisacetamide