Structure-Function Analysis of the HIV-1 Integrase in Complex With Two Cellular Proteins: Ledgf and INI1

Integration of the human immunodeficiency virus type 1 (HIV-1) cDNA into the human genome is catalyzed by the viral integrase protein (IN) that requires cellular cofactors for viral infectivity. Recently, we solved a cryo-EM structure at 14 A resolution of the HIV-1 integrase in complex with the lens epithelium-derived growth factor (LEDGF), a cellular transcriptional coactivator, in presence and absence of DNA (1). This structure revealed the molecular mechanism of DNA integration in the human genome. Another cellular co-factor, the integrase interactor 1 protein (INI1/SNF5) which is a part of the SWI/SNF complex, an ATP dependant chromatin remodeler, has been shown to binds directly to integrase. Its function in the viral DNA integration process is not well characterized, but its presence is critical for viral infectivity. We stably formed, in vitro, a complex comprising IN, LEDGF and a fragment of INI1. In vitro functional assays have been performed and a 15 A resolution cryo-EM structure of the ternary complex has been solved. The structure function analysis and the effect of INI1 on the DNA binding, 3′ processing and integration reaction will be presented.(1) Michel, F., Crucifix, C., Granger, F., Eiler, S., Mouscadet, J.F., Korolev, S., Agapkina, J., Ziganshin, R., Gottikh , M., Nazabal, A., Emiliani, S., Benarous, R., Moras, D., Schultz, P. and Ruff, M. (2009). Structural basis for HIV-1 DNA integration in the human genome, role of the LEDGF/P75 cofactor. EMBO J., 28, 980-991.