Abstract
After HIV integration of the proviral DNA into the host genome, the virus can remain latent or activate
transcription. The viral Tat protein, which enhances transcript elongation from the HIV-1 promoter, is the switch
between these two states. Since Tat resides under the control of the same promoter, it enhances its own
transcription via a positive feedback loop. We identified didehydro-Cortistatin A (dCA) as a very potent
inhibitor of Tat (1, 2). In human CD4 +T cells isolated from aviremic individuals, combining dCA with ART
accelerates HIV-1 suppression and prevents viral rebound during treatment interruption, as the HIV-1 promoter
remains epigenetically repressed. HIV-1 transcriptional inhibitors have the unique property of reducing particle
production from infected cells. dCA is the proof-of-concept that this novel class of molecules is amenable to
block-and-lock functional cure approaches, which aim at reducing residual viremia during ART and limit
viral rebound. It is thus important to understand the mechanisms that explain not only dCA's inhibition of
reactivation, but also mechanisms regulating HIV-1 latency in CD4+T memory T cells in general, to expand on
“block-and-lock” approaches, and explore alternative options for retroviral suppression.
There are approximately 320 human chromatin regulators, which “write”, “erase”, or “read” chromatin
modifications, or remodel nucleosome topology. Specificity in gene expression derives from the combinatorial
nature of chromatin modifications, and assembly of related chromatin regulator subunits. The rationale for this
proposal is that factors that establish HIV-1 latency are important for viral reactivation, and that by identifying
and inhibiting them, a “locked” state of silencing that is exceedingly resistant to reactivation can be achieved.
We propose to combine a comprehensive high-resolution mapping of the nucleosome
organization and positioning of chromatin remodeling complexes at the HIV promoter during HIV
latency, with a robust pooled shRNAs screening approach to interrogate all chromatin regulatory factors
in parallel during a single experiment. Primary and secondary screens will be performed in a newly developed
primary cell system that captures bona fide HIV-1 latency, and departs from CD4+T cells from successfully
treated HIV infected donors.
During the R61 phase of the project we will be able to correlate high-resolution nucleosome
architecture data with their binding to all chromatin remodeling machine families and develop a comprehensive
picture of the signals and factors that drive chromatin activity at the HIV-1 genome during latency. This data
will support robust hypotheses and targets to test in detail during the R33 phase. We anticipate that from these
candidates, we can infer how HIV-latency is controlled and develop rational therapeutic approaches to
modulate HIV latency.