Current antiretroviral therapy can nearly eliminate viremia and most active HIV replication. The potency of future therapies is likely to increase. However, a subpopulation of HIV-infected lymphocytes avoids viral or immune cytolysis and returns to the resting state. This reservoir will persist without new therapeutic approaches. We have defined a mechanism that may establish or maintain viral quiescence in T cells. We have shown that host factors form a complex at the HIV long terminal repeat (LTR) promoter, inhibiting HIV gene expression. LSF recruits YY1 to the LTR. YYI in turn recruits histone deacetylase 1 (HDACI), a chromatin remodeling enzyme that inhibits transcription. Significantly, we have validated the biological relevance of these findings in resting CD4+ cells obtained from HIV+ donors. Using polyamides, synthetic cell-permeable small molecules that bind DNA in a sequence-specific manner and inhibit DNA- protein interactions, we have directly demonstrated inhibition of LSF binding at the LTR and increased LTR expression in T cells. Exposing resting CD4+ cells obtained from aviremic HIV-infected donors to specific polyamides results in HIV outgrowth. To confirm and extend our studies, we will test these hypotheses:
Specific Aim I : To elucidate the regulation of the LSF/YYI/HDACI LTR repressor complex: phosphorylation and acetylation regulate repressor complex assembly.
Specific Aim II : To study the counter-regulation of LTR expression by chromatin-modifying enzymes: HATS and HDACI compete, affecting LTR architecture, and viral and host transcription factor activity.
Specific Aim III : To measure HIV expression after disruption of repressor function in primary cells: Both a novel tool and a potential therapeutic, polyamides allow the study of factors that restrict the expression of HIV within resting CD4+ cells obtained from HIV+ donors. Studies of downregulation of HIV gene expression and the role of host factors in the quiescent, aviremic HIV infection may give insight into general mechanisms of transcriptional regulation, T cell and HIV biology, and lead to rational therapies directed at the persistent reservoir of HIV infection within resting CD4+ T cells.
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