Bloom syndrome helicase is required for efficient HIV-1 reverse transcription in macrophages

The induction of DNA damage by HIV-1 prior to integration suggests a function for DNA damage responses (DDR) during early infection, however what this role is remains incompletely understood. Initial experiments, using specific inhibitors for DDR pathways demonstrate that both ATM and ATR are necessary for efficient HIV-1 infection of macrophages with ATM acting at the late reverse transcription step. To identify DDR factors associated with ATM/ATR pathways that influence HIV-1 infection, a CRISPR knockout screen using a DDR-focused sgRNA library was performed. Approximately 30 DDR genes that impacted HIV-1 infection were identified with 13 factors that facilitated HIV-1 infection and 17 DDR factors that restrict HIV-1 infection. Several hits were factors associated with the Fanconi anemia pathway, such as BTR complex proteins, including the RecQ helicase Bloom syndrome helicase. BLM was specifically demonstrated to enhance HIV-1 infection and replication with knockdown of BLM expression diminishing integration and the establishment of intact HIV-1 proviruses in macrophages by 50%. BLM is associated with HIV-1 late reverse transcription intermediates, the step that proceeds HIV-1 integration. These findings identify BLM as a DDR host factor that promotes early HIV-1 infection by facilitating completion of reverse transcription and subsequent integration.