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

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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.