title: Association of p65 and C/EBPbeta with HIV-1 LTR modulates transcription of the viral promoter.
abstract: In human immunodeficiency virus type 1 (HIV-1) latently infected cells, NF-kappaB (NF-kappaB) plays a critical role in the transcriptional induction of the HIV-1 promoter. The trans-activating ability of NF-kappaB can be modified by another nuclear factor C/EBPbeta that can physically bind to NF-kappaB and regulate its activity. Because the HIV-1 promoter also contains a C/EBPbeta site adjacent to the NF-kappaB site, the present study examined cooperative functional in vivo interaction of the p65 subunit of NF-kappaB and C/EBPbeta, and the impact of Tat in this event. We demonstrated that ectopic expression of p65 along with Tat increases p65 binding to HIV-1 LTR, and that this increase correlates with enhanced HIV-1 promoter activity. Further, co-expression of C/EBPbeta and Tat leads to a decrease in p65 binding, which allows C/EBPbeta to bind more efficiently to the LTR. Inhibition of p65 expression by siRNA significantly decreases C/EBPbeta-binding and LTR expression. Using ChIP assay, we confirmed the existence of an interchange between p65 and C/EBPbeta and their abilities to bind to the LTR in vivo. These observations demonstrate that a delicate balance of interaction between p65, C/EBPbeta, and Tat can dictate the level of HIV-1 LTR transcription.
authors.affiliation: Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, Philadelphia, Pennsylvania 19122, USA.
authors.forename: Ruma
authors.initials: R
authors.lastname: Mukerjee
authors.forename: Bassel E
authors.initials: BE
authors.lastname: Sawaya
authors.forename: Kamel
authors.initials: K
authors.lastname: Khalili
authors.forename: Shohreh
authors.initials: S
authors.lastname: Amini
mesh_terms: D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism*; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D015967:Gene Expression Regulation, Viral; D016325:HIV Long Terminal Repeat / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051996:Transcription Factor RelA / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D022782:CCAAT-Enhancer-Binding Protein-beta; D016328:NF-kappa B; D034741:RNA, Small Interfering; D051996:Transcription Factor RelA; D015500:Chloramphenicol O-Acetyltransferase