BET bromodomain-targeting compounds reactivate HIV from latency via a Tat-independent mechanism

Cell Cycle. 2013 Feb 1;12(3):452-62. doi: 10.4161/cc.23309. Epub 2012 Feb 1.

Abstract

The therapeutic potential of pharmacologic inhibition of bromodomain and extraterminal (BET) proteins has recently emerged in hematological malignancies and chronic inflammation. We find that BET inhibitor compounds (JQ1, I-Bet, I-Bet151 and MS417) reactivate HIV from latency. This is evident in polyclonal Jurkat cell populations containing latent infectious HIV, as well as in a primary T-cell model of HIV latency. Importantly, we show that this activation is dependent on the positive transcription elongation factor p-TEFb but independent from the viral Tat protein, arguing against the possibility that removal of the BET protein BRD4, which functions as a cellular competitor for Tat, serves as a primary mechanism for BET inhibitor action. Instead, we find that the related BET protein, BRD2, enforces HIV latency in the absence of Tat, pointing to a new target for BET inhibitor treatment in HIV infection. In shRNA-mediated knockdown experiments, knockdown of BRD2 activates HIV transcription to the same extent as JQ1 treatment, while a lesser effect is observed with BRD4. In single-cell time-lapse fluorescence microscopy, quantitative analyses across ~2,000 viral integration sites confirm the Tat-independent effect of JQ1 and point to positive effects of JQ1 on transcription elongation, while delaying re-initiation of the polymerase complex at the viral promoter. Collectively, our results identify BRD2 as a new Tat-independent suppressor of HIV transcription in latently infected cells and underscore the therapeutic potential of BET inhibitors in the reversal of HIV latency.

Keywords: BRD2; BRD4; HIV; I-BET; I-BET151; JQ1; MS417; P-TEFb; Tat; latency.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Azepines / pharmacology
  • Benzodiazepines / pharmacology
  • CD4-Positive T-Lymphocytes / virology
  • Cell Cycle Proteins
  • Cells, Cultured
  • HEK293 Cells
  • HIV Infections / virology*
  • HIV-1 / drug effects
  • HIV-1 / genetics
  • HIV-1 / physiology*
  • Heterocyclic Compounds, 4 or More Rings / pharmacology
  • Humans
  • Jurkat Cells
  • Nuclear Proteins / antagonists & inhibitors
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Positive Transcriptional Elongation Factor B / genetics
  • Positive Transcriptional Elongation Factor B / metabolism
  • Promoter Regions, Genetic / drug effects
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA Interference
  • RNA, Small Interfering
  • Transcription Factors / antagonists & inhibitors
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Transcription, Genetic / drug effects
  • Triazoles / pharmacology
  • Virus Latency
  • tat Gene Products, Human Immunodeficiency Virus / genetics
  • tat Gene Products, Human Immunodeficiency Virus / metabolism*

Substances

  • (+)-JQ1 compound
  • Azepines
  • BRD2 protein, human
  • BRD4 protein, human
  • Cell Cycle Proteins
  • GSK1210151A
  • Heterocyclic Compounds, 4 or More Rings
  • Nuclear Proteins
  • RNA, Small Interfering
  • Transcription Factors
  • Triazoles
  • tat Gene Products, Human Immunodeficiency Virus
  • Benzodiazepines
  • molibresib
  • Positive Transcriptional Elongation Factor B
  • Protein-Serine-Threonine Kinases