Functional analyses of mutants of the central core domain of an Avian Sarcoma/Leukemia Virus integrase.

Integrase (IN) is the enzyme responsible for the integration of the retroviral genome into the host cell DNA. Herein, three mutants of conserved residues (V79, S85 and I146) of the central core domain (CCD) of an Avian Sarcoma/Leukemia Virus IN were analyzed in vitro. Our data revealed (i) the inability of S85T mutant to form dimers and tetramers in the absence of DNA and (ii) a slightly reduced ability of V79A IN in tetramers formation. Surprisingly, both mutants were still able to efficiently achieve concerted DNA integration. This could be explained by the ability of the two mutants to form complexes in the presence of DNA. These data suggest a strong structural role of the region encompassing V79 and S85 residues (β2/β3 turn-β3 strands) following binding to viral DNA and highlight the dynamic nature of IN.