Production of a discrete, infectious, double-stranded DNA by reverse transcription in virions of Moloney murine leukemia virus.

One of the most unique viral replication schemes is that of the retroviruses (a class that includes the R N A tumor viruses). These viruses synthesize a doublestranded (DS) D N A copy of their single-stranded (SS) R N A genome as the initial event following infection of susceptible cells (see Weinberg 1977). The details of this process--called reverse transcription--are still obscure, but the general outlines have become clear during the last few years. The study of reverse transcription has proceeded along two lines. Some workers have studied nucleic acid molecules extracted from recently infected cells (Weinberg 1977); others have utilized in vitro systems of reverse transcription either with detergent-activated virions or in reconstructed systems (Verma 1977; Taylor 1977). Although the in vitro systems have been useful in studying individual events of the reverse transcription process, only recently have the systems been perfected to the point where they mimic in vivo results. This paper is concerned with the proof that in vitro systems derived from detergent-activated virions of murine leukemia virus (MuLV) do mimic quite faithfully the events that occur in infected cells. We also describe an unexpected effect of actinomycin D (Act D) on the reverse transcription process and will interpret that effect in the context of a general model of the process of reverse transcription.