Human cell proteins and human immunodeficiency virus DNA integration

Integration, catalyzed by the viral integrase (IN) protein, is a crucial step in the life cycle of all retroviruses including human immunodeficiency virus type 1 (HIV-1). Although purified HIV-1 IN protein is sufficient to catalyze the DNA breakage and joining steps of integration in the absence of any other protein factor, a number of studies indicate that cellular proteins participate in the integration process in cells. These host cell proteins have been proposed to act through binding the pre-integrated viral cDNA substrate, by directly interacting with the IN protein, and/or by repairing the single-stranded DNA gaps that occur at viral/chromosomal DNA junctions during integration. In this paper we summarize the identification and potential roles of specific cell factors in HIV-1 integration. We also present experimental results of human cell proteins that coimmunoprecipitated with HIV-1 IN following its expression in HeLa cells and discuss these results in light of the previously-identified integration cofactors.