RNA-directed DNA polymerase from human leukemic blood cells and from primate type-C virus-producing cells: high- and low-molecular-weight forms with variant biochemical and immunological properties

Abstract

RNA-directed DNA polymerase (reverse transcriptase) from leukocytes of individual leukemic patients can be grouped by velocity gradient analyses into two distinct classes, a low-molecular-weight (LMW) class of approximately 70,000 and a high-molecular-weight (HMW) class of 130,000 to 140,000. The reverse transcriptases from mammalian type-C viruses have with one exception (see text) been isolated as enzymes with molecular weights of 70,000. In this study, the reverse transcriptase from extracellular gibbon ape leukemia virus was also isolated only as the LMW class. However, the enzyme from gibbon virus-producing cells was isolated partially in the HMW form; this form was converted completely to the LMW form by treatment with 0.5 M KC1 and 0.5% Triton X-100 and could be re-converted to the HMW form by lowering the KC1 and Triton X-100 concentrations. A similar conversion from a HMW form to a LMW form was demonstrated with enzyme from human leukemic cells. The LMW form of the human and gibbon ape cellular enzymes utilized synthetic primer-templates in a similar fashion to viral enzyme, and this form was strongly inhibited by antisera (IgG) to reverse transcriptase from simian (woolly monkey) type-C virus. The HMW form of both enzymes utilized synthetic primer-templates less efficiently than the LMW form, and was resistant to inhibition by antipolymerase IgG of simian type-C virus. The HMW form of the cellular reverse transcriptases transcribed viral 70S RNA in the absence of synthetic primer relatively more efficiently than did the extracellular viral form. These data suggest that the HMW form is due in part to aggregation of the LMW form and in part to a cellular factor(s) which may affect both the form and function of intracellular reverse transciptase.