# Characterizing chromatin protein dynamics in HIV-1 latency with a CASPEX approach

> **NIH NIH R21** · ICAHN SCHOOL OF MEDICINE AT MOUNT SINAI · 2022 · $211,250

## Abstract

PROJECT SUMMARY
This project aims to develop and apply CASPEX technologies to measure protein changes in cells latently
infected with HIV-1. CASPEX refers to the combination of a catalytically-dead Cas9 (dCas9) protein that can
localize to a specific genomic locus fused to an engineered ascorbate peroxidase enzyme (APEX2) that is
capable of biotinylating proteins within a sphere of proximity to the fusion protein. CASPEX enables the capture
of proteins and nucleic acids in proximity to a genomic locus defined by guide RNAs complexed with dCas9.
This powerful approach can be combined with mass spectrometry analysis to identify and quantify changes in
proteins associated with genomic loci in an unbiased manner.
HIV-1 latency represents the major barrier to developing new therapies for HIV-1 treatment and cure. The
molecular processes governing HIV-1 latency have been investigated using high-throughput genetics, small
molecule screening, and focused molecular biology studies. CASPEX has the potential to provide
complementary information regarding HIV-1 latency processes that can confirm prior work or open new avenues
of research. In this project, we will develop two CASPEX approaches and apply them to models of HIV-1 latency.
In Specific Aim 1, we will engineer cell line models of HIV-1 latency for CASPEX analysis and characterize
protein changes at integrated HIV-1 chromatin loci in response to latency reversal. Findings made in cell line
models of HIV-1 latency are not always recapitulated in vivo, so in Specific Aim 2 we will develop a novel
approach to apply CASPEX in primary CD4+ T cells. Successful completion of this project will advance the
molecular understanding of HIV-1 latency and latency reversal, potentially informing on the development of next-
generation therapies to treat or cure HIV-1 infection.

## Key facts

- **NIH application ID:** 10547359
- **Project number:** 1R21AI172554-01
- **Recipient organization:** ICAHN SCHOOL OF MEDICINE AT MOUNT SINAI
- **Principal Investigator:** Jeffrey R Johnson
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $211,250
- **Award type:** 1
- **Project period:** 2022-08-08 → 2024-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10547359

## Citation

> US National Institutes of Health, RePORTER application 10547359, Characterizing chromatin protein dynamics in HIV-1 latency with a CASPEX approach (1R21AI172554-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10547359. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*