Synthesis of virus-specific high-mobility DNA after temperature upshift ofSC-1 cells chronically infected with moloney murine leukemia virus mutant ts1

Premature termination products of reverse transcription that consist physic ally of viral minus-sense single-stranded DNA that is shorter than one long terminal repeat and partial DNA duplexes are dramatically increased in the central nervous system (CNS) of FVB/N mice that are infected by ts1, a tem perature-sensitive mutant of Moloney murine leukemia virus. Due to their mi gration in agarose gels, these incomplete physical forms of DNA have been d esignated high-mobility (HM) DNA, In non-CNS tissues, the level of HM DNA i s either low or not detectable. In order to determine the conditions that a re necessary for the synthesis of HM DNA in vivo, we have characterized the physical forms of HM DNA that were synthesized in vitro in chronically inf ected SC-1 cells after temperature upshift, At the permissive temperature o f 34 degrees C, the chronically infected SC-1 cells did not synthesize HM D NA. After temperature upshift of the cultured cells from 34 to 37 degrees C , the chronically infected SC-1 cells developed extremely high levels of HM DNA, Following temperature downshift of the cultured cells from 37 to 34 d egrees C, a decrease in the level of HM DNA and an increase in the level of unintegrated linear proviral DNA occurred simultaneously. These results su ggested that the accumulation of HM DNA both in vitro and in vivo may be th e result of superinfection.