Mapping HIV-1 and PFV intasome integration sites in chromatinized Widom-601 arrays
HIV-1 and other lentiviruses hijack the cellular chromatin-binding protein LEDGF/p75 to facilitate integration into active transcription units. However, the mechanism of chromatin engagement by lentiviral intasomes and the structural role of LEDGF/p75 in this process remain poorly understood. To address these gaps, we studied the activities of in vitro-assembled retroviral intasomes in the presence of chromatinized target DNA. While LEDGF/p75 was both essential and minimally sufficient to enhance lentiviral integration into chromatin containing histone H3 trimethylated on Lys36, it unexpectedly facilitated integration outside of the nucleosome core particles. LEDGF/p75 additionally inhibited integration into unmodified chromatin in a dose-dependent manner, promoting integration into naked DNA. The results establish the preference of lentiviral intasomes for linker DNA regions within H3K36Me3-enriched chromatin.