SummaryAn oligo (dT) primed terminM transferase-like activity was demonstrable with a number of disrupted mammalian retroviruses and the soluble reverse transcriptases therefrom. The characteristics of this activity were consistent with it being due to reverse transcriptase.
*Terminal transfer of deoxynueleotides to a deoxynuclcotide primer and replicative template dependent copying of an 1%NA or DNA template are generally thought to be distinct enzymatic functions catalysed by terminal transferase (TdT) (3) and RNA-or, DNA-directed DNA polymerase (11--t3), respectively. The demonstration of primer dependent deoxynueleotide polymerisation by disrupted retroviruses was originally (2) thought to reflect the presence of a virion-associated TdT but was subsequently (8) attributed to the action of reverse transcriptase (RT) on newly generated templates. We observed a similar type of primer stimulated activity in disrupted L cell virions (LCV) but this activity was retained by a partially purified presumptive reverse transcriptase from this particle. We have now found that the partially purified reverse transcriptases from a number of retroviruses also manifest this unusual activity. It may be that this terminal transferase-like activity is not a templated reaction but is a trne terminal transfer thus implying a single enzyme can catalyse two distinct reactions.Reagents were obtained as described previously (6). The virus associated DNA polymerase was parially purified by DEAE-cellulose chromotography and assayed, essentially as previously described (6).Purified retroviruses, when disrupted by detergent and incubated in the presence of laHI-TTP and otigo (dT) incorporated substantial amounts of labelled precursor into an acid insoluble product (Table 1), as described by other workers (2,8).