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

• Published in: The Journal of biological chemistry Vol. 290; no. 45; pp. 27297 - 27310
• Main Authors: Huang, Huachao, Santoso, Netty, Power, Derek, Simpson, Sydney, Dieringer, Michael, Miao, Hongyu, Gurova, Katerina, Giam, Chou-Zen, Elledge, Stephen J., Zhu, Jian
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 06.11.2015; American Society for Biochemistry and Molecular Biology
• Subjects: CD4 T cell; 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; FACT complex; HEK293 Cells; High Mobility Group Proteins - antagonists & inhibitors; High Mobility Group Proteins - genetics; High Mobility Group Proteins - physiology; HIV Long Terminal Repeat; HIV-1 - genetics; HIV-1 - physiology; host-pathogen interaction; Host-Pathogen Interactions - genetics; Host-Pathogen Interactions - physiology; human immunodeficiency virus (HIV); Human T-lymphotropic virus 1 - genetics; Human T-lymphotropic virus 1 - physiology; Humans; latency; Microbiology; Models, Biological; Positive Transcriptional Elongation Factor B - physiology; Promoter Regions, Genetic; RNA Interference; RNA interference (RNAi); SSRP1; SUPT16H; Transcription Factors - antagonists & inhibitors; Transcription Factors - genetics; Transcription Factors - physiology; transcription repressor; Transcriptional Elongation Factors - antagonists & inhibitors; Transcriptional Elongation Factors - genetics; Transcriptional Elongation Factors - physiology; viral transcription; Virus Latency - genetics; Virus Latency - physiology; host-pathogen interaction; RNA interference (RNAi); FACT complex; SUPT16H; human immunodeficiency virus (HIV); viral transcription; latency; CD4 T cell; transcription repressor; SSRP1
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M115.652339

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. Background: FACT proteins SUPT16H and SSRP1 are identified as host factors that restrict HIV-1 replication. Results: Biochemical and genetic evidences that SUPT16H and SSRP1 affect HIV-1/HTLV-1 transcription and latency are provided. Conclusion: SUPT16H and SSRP1 suppress transcription of HIV-1/HTLV-1, and their presence may promote HIV-1 latency. Significance: Identification of host factors necessary for HIV-1 latency is critical, which may benefit the development of novel HIV-1 latency-reversing agents.