EXOGENOUS NUCLEOSIDES PROMOTE THE COMPLETION OF MOMLV DNA-SYNTHESIS IN G0-ARRESTED BALB-C 3T3 FIBROBLASTS/

We studied Moloney murine leukemia virus replication in newly infected Balb c/3T3 cells brought to the GO phase by serum depletion. Using th e polymerase chain reaction method, we showed that Moloney murine leuk emia virus can be efficiently internalized in nonproliferating fibrobl asts, although reverse transcription of the viral RNA in these cells r emains uncompleted. It seems likely that a lower availability of deoxy ribonucleotides in GO-arrested cells is responsible for this premature termination of the reverse transcription step. Accordingly, the addit ion of high concentrations of nucleosides to the culture medium of non dividing cells simultaneously with infection enables them to complete the reverse transcription process, without reinitiating the cell cycle . Inhibition of reverse transcription by hydroxyurea confirms the depe ndence of this retroviral step on the intracellular nucleotide pool ra ther than on the precise arrest point of the host cell cycle. Furtherm ore, the pyrimidine nucleotide pool, and more particularly the cytidin e pool, appears to play a central regulatory role in this step. (C) 19 94 Academic Press, Inc.