NF-κB p50 promotes HIV latency through HDAC recruitment and repression of transcriptional initiation

Abstract

Cells latently infected with HIV represent a currently insurmountable barrier to viral eradication in infected patients. Using the J‐Lat human T‐cell model of HIV latency, we have investigated the role of host factor binding to the κB enhancer elements of the HIV long terminal repeat (LTR) in the maintenance of viral latency. We show that NF‐κB p50–HDAC1 complexes constitutively bind the latent HIV LTR and induce histone deacetylation and repressive changes in chromatin structure of the HIV LTR, changes that impair recruitment of RNA polymerase II and transcriptional initiation. Knockdown of p50 expression with specific small hairpin RNAs reduces HDAC1 binding to the latent HIV LTR and induces RNA polymerase II recruitment. Similarly, inhibition of histone deacetylase (HDAC) activity with trichostatin A promotes binding of RNA polymerase II to the latent HIV LTR. This bound polymerase complex, however, remains non‐processive, generating only short viral transcripts. Synthesis of full‐length viral transcripts can be rescued under these conditions by expression of Tat. The combination of HDAC inhibitors and Tat merits consideration as a new strategy for purging latent HIV proviruses from their cellular reservoirs.

Transcriptional burst frequency and burst size are equally modulated across the human genome

“…5C and D), and the use of TSA, which induces expression through a different mechanism than TNF (32), corroborates this observation (SI Appendix). This observed decrease in k off with TNF induction leads to extended duration of bursts and is consistent with the reported inhibition of p50-HDAC1 repressivecomplex formation at LTR NFκB sites by p50/RelA heterodimers (33)-the successful formation of HDAC1 leads to weakened recruitment of RNA polymerase II and weakened transcriptional initiation (34). The observed increases in k on are also consistent with increased recruitment of RNA polymerase II to the LTR promoter NFκB sites induced by TNF (35,36).…”

Double Plant Homeodomain (PHD) Finger Proteins DPF3a and -3b Are Required as Transcriptional Co-activators in SWI/SNF Complex-dependent Activation of NF-κB RelA/p50 Heterodimer

“…Similar amounts of NF-B p50 subunit were detected both before and after TNF-␣ stimulation, which we think is consistent with previous observations that low levels of the p50 subunit are present on specific NF-B-responsive promoters in the nucleus of unstimulated cells as the p50 homodimer, whereas the majority of this subunit is retained in the cytoplasm as RelA/p50 (33)(34)(35). The p50 homodimer itself does not contain transactivation domains, but it associates with promoter regions of some NF-B-dependent genes, including integrated HIV-1 LTR in the unstimulated conditions (36). However, Brm, BRG1, and DPF3 were all detected at the promoter even before stimulation, and their recruitment levels were not significantly changed upon exposure to TNF-␣, apart from Brm, which showed elevated levels at the promoter (right panel of Fig.…”

Closed Chromatin Architecture Is Induced by an RNA Duplex Targeting the HIV-1 Promoter Region

“…This change occurred within 24 h and was sustained for 11 days. This is particularly significant because previous studies have demonstrated that elevated levels of HDAC1 are associated with the 5Ј-LTR of latent forms of HIV-1 and repressive changes in chromatin structure of the HIV-1 promoter region (41)(42)(43)(44)(45)(46)(47)(48). In contrast, prom-D induced a less marked recruitment of HDAC1 at day 1.…”