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J Biol Chem. 2015 Nov 6;290(45):27297-310. doi: 10.1074/jbc.M115.652339. Epub 2015 Sep 16.

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

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From the Departments of Microbiology and Immunology.
the School of Arts and Sciences, University of Rochester, Rochester, New York 14627.
Department of Biostatistics and Computational Biology, University of Rochester Medical Center, Rochester, New York 14642.
the Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York 14263.
the Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814.
the Division of Genetics, Brigham and Women's Hospital, Howard Hughes Medical Institute, Boston, Massachusetts 02115, and the Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115.
From the Departments of Microbiology and Immunology, Biochemistry and Biophysics, and


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.


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

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