The integration of the retroviral genome into the chro-matin of the infected cell is catalysed by the inte-grase (IN)•viral DNA complex (intasome). This pro-cess requires functional association between theintegration complex and the nucleosomes. Directintasome/histone contacts have been reported tomodulate the interaction between the integrationcomplex and the target DNA (tDNA). Both prototypefoamy virus (PFV) and HIV-1 integrases can directlybind histone amino-terminal tails. We have furtherinvestigated this final association by studying the ef-fect of isolated histone tails on HIV-1 integration. Weshow here that the binding of HIV-1 IN to a peptidederived from the H4 tail strongly stimulates integra-tion catalysisin vitro. This stimulation was not ob-served with peptide tails from other variants or withalpha-retroviral (RAV) and spuma-retroviral PFV in-tegrases. Biochemical analyses show that the pep-tide tail induces both an increase in the IN oligomer-ization state and affinity for the target DNA, whichare associated with substantial structural rearrange-ments in the IN carboxy-terminal domain (CTD) ob-served by NMR. Our data indicate that the H4 peptidetail promotes the formation of active strand transfercomplexes (STCs) and support an activation step ofthe incoming intasome at the contact of the histonetail.< Leer menos