Regulation of HIV-1 gene expression by histone acetylation and factor recruitment at the LTR promoter.
In HIV-1 infected cells, the LTR promoter, once organized into chromatin, is transcriptionally inactive in the absence of stimulation. To examine the chromosomal events involved in transcriptional activation, we analyzed histone acetylation and factor recruitment at contiguous LTR regions by a quantitative chromatin immunoprecipitation assay. In chronically infected cells treated with a phorbol ester, we found that acetylation of both histones H3 and H4 occurs at discrete nucleosomal regions before the onset of viral mRNA transcription. Concomitantly, we observed the recruitment of known cellular acetyl-transferases to the promoter, including CBP, P/CAF and GCN5, as well as that of the p65 subunit of NF-kappa B. The specific contribution of the viral Tat transactivator was assayed in cells harboring the sole LTR. We again observed nucleosomal acetylation and the recruitment of specific co-factors to the viral LTR upon activation by either recombinant Tat or a phorbol ester. Strikingly, P/CAF was found associated with the promoter only in response to Tat. Taken together, these results contribute to the elucidation of the molecular events underlying HIV-1 transcriptional activation.
Lusic
Marina
M
Molecular Medicine Laboratory, International Centre for Genetic Engineering and Biotechnology, Trieste, Italy.
Marcello
Alessandro
A
Cereseto
Anna
A
Giacca
Mauro
M
D000107:Acetylation; D000123:Acetyltransferases / Q000378:metabolism; D002460:Cell Line; D015967:Gene Expression Regulation, Viral; D016325:HIV Long Terminal Repeat / Q000235:genetics*; D015497:HIV-1 / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D051548:Histone Acetyltransferases; D006657:Histones / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D009000:Monocytes; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D016662:Virus Integration / Q000187:drug effects; D017735:Virus Latency / Q000187:drug effects
D006657:Histones; D000123:Acetyltransferases; D051548:Histone Acetyltransferases; D013755:Tetradecanoylphorbol Acetate