Stem-loop binding protein is a multifaceted cellular regulator of HIV-1 replication
Ming Li, … , Michelle A. Lally, Bharat Ramratnam
Ming Li, … , Michelle A. Lally, Bharat Ramratnam
Published July 25, 2016
Citation Information: J Clin Invest. 2016;126(8):3117-3129. https://doi.org/10.1172/JCI82360.
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Research Article AIDS/HIV

Stem-loop binding protein is a multifaceted cellular regulator of HIV-1 replication

Abstract

A rare subset of HIV-1–infected individuals is able to maintain plasma viral load (VL) at low levels without antiretroviral treatment. Identifying the mechanisms underlying this atypical response to infection may lead to therapeutic advances for treating HIV-1. Here, we developed a proteomic analysis to compare peripheral blood cell proteomes in 20 HIV-1–infected individuals who maintained either high or low VL with the aim of identifying host factors that impact HIV-1 replication. We determined that the levels of multiple histone proteins were markedly decreased in cohorts of individuals with high VL. This reduction was correlated with lower levels of stem-loop binding protein (SLBP), which is known to control histone metabolism. Depletion of cellular SLBP increased promoter engagement with the chromatin structures of the host gene high mobility group protein A1 (HMGA1) and viral long terminal repeat (LTR), which led to higher levels of HIV-1 genomic integration and proviral transcription. Further, we determined that TNF-α regulates expression of SLBP and observed that plasma TNF-α levels in HIV-1–infected individuals correlated directly with VL levels and inversely with cellular SLBP levels. Our findings identify SLBP as a potentially important cellular regulator of HIV-1, thereby establishing a link between histone metabolism, inflammation, and HIV-1 infection.

Authors

Ming Li, Lynne D. Tucker, John M. Asara, Collins K. Cheruiyot, Huafei Lu, Zhijin J. Wu, Michael C. Newstein, Mark S. Dooner, Jennifer Friedman, Michelle A. Lally, Bharat Ramratnam

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Figure 3

Histone-related stem-loop binding protein serves as an HIV-1 host factor.

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Histone-related stem-loop binding protein serves as an HIV-1 host factor...
(A) SILAC-MS data were validated by conventional Western blots. Similar to SILAC-MS results, densitometric analysis of the 3 identified histones (H2AZ, H2B1N, and H4) revealed decreased expression in the high-VL cohort in both groups of subjects. β-Actin (ACTB) was used as a loading control. The fold changes in protein levels are noted on the right of their respective gels. (B) RNA levels of the 3 histones (H2AZ, H2B1N, H4) were significantly underexpressed (30%–55%) in pooled VLhigh samples from both groups. (C) Stem-loop binding protein (SLBP), a master regulator of histones, was underexpressed (~50% by densitometric analysis) in pooled VLhigh samples in both groups. (D) SLBP depletion by SMARTpool siRNA (“SLBP”) or individual siRNA (“SLBP-a”–“SLBP-d”) led to higher (1.4- to 2.7-fold) β-gal readings in phase I (n = 3 biologic replicates). (E) SLBP depletion had no significant effects on phase II (n = 3 biologic replicates). The SLBP β-gal results were similar to those obtained from individual histone depletion. Student’s t test; *P < 0.05, **P < 0.01; error bars represent ± SD.