RNase H activity associated with bacterially expressed reverse transcriptase of human T-cell lymphotropic virus III/lymphadenopathy-associated virus.

The reverse transcriptase polymerase of the human T-cell lymphotropic virus/lymphadenopathy-associated virus has been cloned into an expression vector and expressed in Escherichia coli. Two polypeptides of 66 and 51 kDa molecular mass are detectable in polymerase-expressing bacterial lysates with human patient sera. They are processed from a short-lived 120-kDa polyprotein precursor equivalent to a region consisting of polymerase, protease, and endonuclease. The 51 kDa protein appears to originate from the 66-kDa molecule; additional processing products are 32- and 15-kDa proteins. The bacterially expressed polymerase is enzymatically active and exhibits the template specificities, ion requirements, and response to inhibitors of the authentic enzyme. It was purified by DEAE-cellulose-, phosphocellulose-, and poly(rC)-agarose column chromatography followed by glycerol density gradient centrifugation. It copurifies with an RNase H activity, suggesting the existence of a virus-coded DNA polymerase-RNase H complex. The purified bacterial enzyme allows a safe large-scale screening for inhibitors of both activities.