Project description:HIV-1 integration introduces ectopic transcription factor binding sites into host chromatin. We postulate that the integrated provirus serves as an ectopic enhancer that recruits additional transcriptional factors to the integration locus, increases chromatin accessibility, changes 3D chromatin interactions, and enhances both retroviral and host gene expression. We used 4 well-characterized HIV-1-infected cell line clones having unique integration sites and low to high levels of HIV-1 expression. Using single-cell DOGMA-seq, which captured the heterogeneity of HIV-1 expression and host chromatin accessibility, we found that HIV-1 transcription correlated with HIV-1 accessibility and host chromatin accessibility. HIV-1 integration increased local host chromatin accessibility within ~5–30 kb distance. CRISPRa and CRISPRi-mediated HIV-1 promoter activation and inhibition confirmed integration site-dependent HIV-1-driven changes of host chromatin accessibility. HIV-1 did not drive chromatin confirmation changes at the genomic level (by Hi-C) or the enhancer connectome (by H3K27Ac HiChIP). Using 4C-seq to interrogate HIV-1-chromatin interactions, we found that HIV-1 interacted with host chromatin ~100–300 kb from the integration site. By identifying chromatin regions having both increased transcription factor activity (by ATAC-seq) and HIV-1-chromtain interaction (by 4C-seq), we identified enrichment of ETS, RUNT, STAT, and ZNF transcription factor binding that may mediate HIV-1-host chromatin interactions. Our study found that HIV-1 promoter activity increased host chromatin accessibility, increased HIV-1-host chromatin interactions in an integration site dependent manner, within the existing chromatin boundaries without impacting broader host chromatin structure.
Project description:Despite effective antiretroviral therapy (ART), HIV-1 persists as an integrated DNA provirus in the genome of infected cells. Host cells can regulate HIV-1 transcription at the HIV-1 integration site dependent on the location (actively transcribed genes vs repressive chromatin) and the orientation (in the same vs opposite orientation of the host gene transcription) of HIV-1 integration. Presumably, HIV-1 follows the host gene transcriptional activity at the HIV-1 integration site. We interrogated HIV-1-host gene transcriptional interactions at the HIV-1 integration site using CRISPR-mediated activation and inhibition of the host genes (in which HIV-1 was integrated) in seven HIV-1-infected Jurkat T cell clones with known HIV-1 integration sites in the introns of actively transcribed genes and a non-genic region. Using ATAC-seq and strand-specific RNA-seq to examine chromatin accessibility and RNA transcription levels, we found that host gene activation did not increase HIV-1 transcription, while host gene inhibition did not decrease HIV-1 transcription. HIV-1 drove high levels of aberrant host RNA transcription regardless of the HIV-1 integration orientation. HIV-1-driven aberrant host RNA transcription was inhibited by CRISPR-mediated HIV-1 inhibition but not by CRISPR-mediated host gene activation or inhibition. When HIV-1 was integrated into a non-genic region, HIV-1 increased host chromatin accessibility and drove high levels of aberrant host RNA transcription. Overall, HIV-1 LTR promoter-driven transcriptional activity dominated over the host promoter activity. HIV-1 transcription does not passively follow host gene activity. Our results highlight that despite effective ART, silencing HIV-1 promoter is required to inhibit HIV-1-driven aberrant host gene expression and chronic immune activation.
Project description:In order to identify novel factors associated with regulation of HIV-1 transcription, we completed a genome-wide CRISPRi screen in a monogenic model of HIV-1. We identified SLTM mediated suppression of HIV-1 transcription. We hypothesized that SLTM would alter the chromatin acessibility at the site of HIV-1 integration. We conducted ATAC-seq of CRISPR ready cells encoding a single HIV-1 provirus in the SPECC1 gene transduced with a gRNA targetting SLTM and a Non-Targeting gRNA. We found that SLTM knockdown increased HIV-1 proviral acessibility across the provirus and host acessibility downstream of the site of HIV-1 integration.