Catalytic activities of the human T-cell leukemia virus type II integrase

Despite the widespread nature of HTLV-II in New World populations and intravenous drug users, the enzymatic activities of the pol genes have not been reported. To ascertain the activity of the HTLV-II(G12) integrase (IN), the coding region was isolated and the encoded protein was purified, using nickel-affinity chromatography, to greater than 90% homogeneity. HTLV-II(G12) IN proved active on HTLV-II(G12) and HIV-1 integration and disintegration substrates. Distinct differences in requirements for enzyme concentration for 3'-processing, strand-transfer, and disintegration reactions were observed. Catalysis of integration reactions occurred in the presence of either Mn2+ or Mg2+, although strand-transfer activity preferred Mn2+. In comparison, HTLV-II(G12) IN catalyzed disintegration reactions with almost 10-fold less protein, was not selective for Mn2+ or Mg2+, and tolerated higher NaCl concentrations than integration. HTLV-II(G12) IN was unable to catalyze the "splicing" reaction, which suggests that this may not be an activity ubiquitous to all retroviral integrases.