ACTIVITIES OF THE FELINE IMMUNODEFICIENCY VIRUS INTEGRASE PROTEIN PRODUCED IN ESCHERICHIA-COLI

Retroviral DNA integration requires the activity of at least one vital protein, the integrase (IN) protein. We cloned and expressed the inte grase gene of feline immunodeficiency virus (FIV) in Escherichia coli as a fusion to the malE gene and purified the IN fusion protein by aff inity chromatography. The protein is active in site-specific cleavage of the vital DNA ends, DNA strand transfer, and disintegration. FIV IN has a relaxed viral DNA substrate requirement: it cleaves and integra tes FIV DNA termini, human immunodeficiency virus DNA ends, and Molone y murine leukemia virus DNA ends with high efficiencies. In the cleava ge reaction, IN exposes a specific phosphodiester bond near the viral DNA end to nucleophilic attack. In vitro, either H2O, glycerol, or the 3' OH group of the viral DNA terminus can serve as nucleophile in thi s reaction. We found that FIV IN preferentially uses the 3' OH ends of the viral DNA as nucleophile, whereas HIV IN protein preferentially u ses H2O and glycerol as nucleophiles.