FACT Proteins, SUPT16H and SSRP1, Are Transcriptional Suppressors of HIV-1 and HTLV-1 That Facilitate Viral Latency

J Biol Chem. 2015 Nov 6;290(45):27297-27310. doi: 10.1074/jbc.M115.652339. Epub 2015 Sep 16.


Our functional genomic RNAi screens have identified the protein components of the FACT (facilitates chromatin transcription) complex, SUPT16H and SSRP1, as top host factors that negatively regulate HIV-1 replication. FACT interacts specifically with histones H2A/H2B to affect assembly and disassembly of nucleosomes, as well as transcription elongation. We further investigated the suppressive role of FACT proteins in HIV-1 transcription. First, depletion of SUPT16H or SSRP1 protein enhances Tat-mediated HIV-1 LTR (long terminal repeat) promoter activity. Second, HIV-1 Tat interacts with SUPT16H but not SSRP1 protein. However, both SUPT16H and SSRP1 are recruited to LTR promoter. Third, the presence of SUPT16H interferes with the association of Cyclin T1 (CCNT1), a subunit of P-TEFb, with the Tat-LTR axis. Removing inhibitory mechanisms to permit HIV-1 transcription is an initial and key regulatory step to reverse post-integrated latent HIV-1 proviruses for purging of reservoir cells. We therefore evaluated the role of FACT proteins in HIV-1 latency and reactivation. Depletion of SUPT16H or SSRP1 protein affects both HIV-1 transcriptional initiation and elongation and spontaneously reverses latent HIV-1 in U1/HIV and J-LAT cells. Similar effects were observed with a primary CD4+ T cell model of HIV-1 latency. FACT proteins also interfere with HTLV-1 Tax-LTR-mediated transcription and viral latency, indicating that they may act as general transcriptional suppressors for retroviruses. We conclude that FACT proteins SUPT16H and SSRP1 play a key role in suppressing HIV-1 transcription and promoting viral latency, which may serve as promising gene targets for developing novel HIV-1 latency-reversing agents.

Keywords: CD4 T cell; FACT complex; RNA interference (RNAi); SSRP1; SUPT16H; host-pathogen interaction; human immunodeficiency virus (HIV); latency; transcription repressor; viral transcription.

Publication types

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

MeSH terms

  • CD4-Positive T-Lymphocytes / physiology
  • CD4-Positive T-Lymphocytes / virology
  • Cell Cycle Proteins / antagonists & inhibitors
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / physiology*
  • Cell Line
  • Cyclin T / physiology
  • DNA-Binding Proteins / antagonists & inhibitors
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / physiology*
  • HEK293 Cells
  • HIV Long Terminal Repeat
  • HIV-1 / genetics
  • HIV-1 / physiology*
  • High Mobility Group Proteins / antagonists & inhibitors
  • High Mobility Group Proteins / genetics
  • High Mobility Group Proteins / physiology*
  • Host-Pathogen Interactions / genetics
  • Host-Pathogen Interactions / physiology
  • Human T-lymphotropic virus 1 / genetics
  • Human T-lymphotropic virus 1 / physiology*
  • Humans
  • Models, Biological
  • Positive Transcriptional Elongation Factor B / physiology
  • Promoter Regions, Genetic
  • RNA Interference
  • Transcription Factors / antagonists & inhibitors
  • Transcription Factors / genetics
  • Transcription Factors / physiology*
  • Transcriptional Elongation Factors / antagonists & inhibitors
  • Transcriptional Elongation Factors / genetics
  • Transcriptional Elongation Factors / physiology*
  • Virus Latency / genetics
  • Virus Latency / physiology*


  • CCNT1 protein, human
  • Cell Cycle Proteins
  • Cyclin T
  • DNA-Binding Proteins
  • High Mobility Group Proteins
  • SSRP1 protein, human
  • SUPT16H protein, human
  • Transcription Factors
  • Transcriptional Elongation Factors
  • Positive Transcriptional Elongation Factor B