# Control of P-TEFb biogenesis and HIV transcription in primary T-cells

> **NIH NIH R01** · CASE WESTERN RESERVE UNIVERSITY · 2021 · $402,500

## Abstract

Our understanding of HIV latency and persistence has been complicated by the small numbers
of latently infected cells found in the circulation, the difficulty of obtaining comprehensive sets of
tissue samples from patients, the lack of known phenotypic markers that can distinguish latently
infected cells from uninfected ones, and limited information about the behavior of tissue reservoirs
in vivo. Mechanistic studies, conducted primarily using cell line models of HIV latency, have
shown that viral reactivation requires transactivation of epigenetically silenced proviruses by the
viral Tat protein in complex with the host transcription elongation co-factors P-TEFb and the super
elongation complex (SEC). Crucially for the study of HIV latency, additional P-TEFb control
mechanisms exist in resting memory CD4+ T cells, where CycT1 protein levels are drastically
reduced. We have also recently shown in primary T cells that CDK9 is present in an inactive state
bound to Hsp90/Cdc37. Therefore, specific T-cell signaling pathways need to be activated in order
to assemble a functional 7SK snRNP complex in primary cells. Using a refined highly reproducible
primary cell model of HIV latency (the QUECEL model), we will address two key unsolved, but
fundamental, questions on the transcriptional control of HIV latency: (1) How do T-cell signaling
pathways regulate the assembly of P-TEFb, 7SK snRNP and the SEC in memory CD4+ T cells?
(2) What Tat-dependent and independent T-cell molecular mechanisms allow for the exchange
of P-TEFb from 7SK snRNP to the SEC and eventually to the latent HIV provirus? Our specific
aims will investigate the regulation of the biogenesis and disassembly of 7SK snRNP by post-
translational modifications and T-cell signaling pathways (Aim 1), apply fluorescence imaging of
the spatiotemporal distribution and delivery of P-TEFb to the latent provirus (Aim 2) and define
the biochemistry of the exchange of P-TEFb from 7SK snRNP during proviral reactivation (Aim
3). The key technological breakthrough, which distinguishes this work from virtually all previous
studies of HIV transcription regulation is that we now have available reliable primary cell models
for HIV latency and reactivation. Working with primary cells can be challenging since relatively
limited numbers of cells are available. We therefore emphasize the use of imaging experiments
and highly sensitive ChIP-Seq and RNA-Seq assays in the majority of our experiments. Defining
the molecular and cell biological mechanisms leading to P-TEFb biogenesis and its transfer to
the HIV promoter should provide the definitive identification of the pharmacological targets that is
needed for the development of new and efficient classes of latency reversing agents.

## Key facts

- **NIH application ID:** 10158438
- **Project number:** 5R01AI148083-03
- **Recipient organization:** CASE WESTERN RESERVE UNIVERSITY
- **Principal Investigator:** JONATHAN KARN
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $402,500
- **Award type:** 5
- **Project period:** 2019-06-01 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10158438

## Citation

> US National Institutes of Health, RePORTER application 10158438, Control of P-TEFb biogenesis and HIV transcription in primary T-cells (5R01AI148083-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10158438. Licensed CC0.

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