The integrase interactor I (INII) proteins facilitate Tat-mediated human immunodeficiency virus type I transcription

Integration of human immunodeficiency virus type 1 ( HIV-1) into the host genome is catalyzed by the viral integrase ( IN) and preferentially occurs within transcriptionally active genes. During the early phase of HIV-1 infection, the incoming viral preintegration complex ( PIC) recruits the integrase interactor 1 ( INII)/hSNF5, a chromatin remodeling factor which directly binds to HIV-1 IN. The impact of this event on viral replication is so far unknown, although it has been hypothesized that it could tether the preintegration complex to transcriptionally active genes, thus contributing to the bias of HIV integration for these regions of the genome. Here, we demonstrate that while INII is dispensable for HIV-1 transduction, it can facilitate HIV-1 transcription by enhancing Tat function. INII bound to Tat and both the repeat ( Rpt) 1 and Rpt 2 domains of INII were required for efficient activation of Tat-mediated transcription. These results suggest that the incoming PICs might recruit INII to facilitate proviral transcription.