PSIP1/LEDGF reduces R-loops at transcription sites and maintain genome integrity (CUT&Tag-Seq)

R-loops are transcriptional by-products that pose a persistent threat to genome integrity and are implicated in accelerated ageing and cancer. PSIP1/LEDGF is a multifunctional chromatin protein that associates with transcriptional elongation machinery. Here, we demonstrated that PSIP1 interacts with R-loops generated at the site of transcription and along with the factors involved in R-loop resolution, including PARP1. Reduced PSIP1 levels in human and mouse cells lead to an increase in R-loop levels and DNA damage at the PSIP1 binding sites. This increased R-loops and DNA damage was specific at the RNA polymerase II transcription sites, causing local transcriptional arrest. In addition, we demonstrate that PSIP1 can be targeted for increasing the sensitivity of cancer cells to PARP1 inhibitors and transcription-coupled DNA damaging agents. These findings show the critical role of PSIP1 in reducing the R-loop burden and DNA damage at the transcriptionally active regions of the genome. Cleavage Under Targets and Tagmentation DNA-sequencing (CUT&Tag-Seq) for PSIP1, S9.6, gammaH2AX and IgG in RWPE-1 cells transduced with control shRNAs or PSIP1 sh RNAs. For each group, samples were processed in a minimum of two biological replicates.