Characterization of intracellular reverse transcription complexes of Moloney murine leukemia virus

To examine the early events in the life cycle of Moloney murine leukemia vi rus (MoMLV), we analyzed the intracellular complexes mediating reverse tran scription. Partial purification of the reverse transcription complexes (RTC s) by equilibrium density fractionation and velocity sedimentation indicate d that three distinct species of intracellular complexes are formed shortly after cell infection. Only one of these species is able to start and compl ete reverse transcription in the cell cytoplasm, This RTC is composed of at least the viral genome, capsid, integrase, and reverse transcriptase prote ins. The RTC becomes permeable to micrococcal nuclease but not to antibodie s. Shortly after initiation of reverse transcription, the viral strong stop DNA within the RTC is protected from nuclease digestion. The sedimentation velocity of the RTC decreases during reverse transcription. After entry in to the nucleus, most capsid proteins are lost from the RTC and its sediment ation velocity decreases further.