In vitro uptake of tritium from uridine-5-H3 into RNA (and DNA) in normal and murine leukemia virus infected mouse embryo tissue

Abstract

The multiplication and release into the medium of a murine leukemic virus (GC) occurs in mouse embryo tissue cultures. Autoradiographic analysis of such infected and uninfected cultures after 24-h labeling periods with uridine-5-H3 demonstrated extensive nuclear and cytoplasmic activity. Such activity was always more extensive in infected cultures, indicating that they were more metabolically active than uninfected cultures. The cytoplasmic activity was apparently in single-stranded RNA, since it was completely removed with pancreatic RNase. A portion of the nuclear label which was RNase-resistant was in DNA, since RNase followed by DNase, or the reverse, removed all label.Autoradiographic analysis of cultures given pulse labels of uridine-5-H3 from 5 to 60 min revealed only nuclear label, always more extensive in infected cultures. This indicates that the synthesis of "rapidly labeled" RNA is enhanced by viral infection; this occurs even within 2 h after infection. Nuclear activity observed after 5- and 10-min pulses was removed by buffers containing RNase or DNase. Possibly this label was in diffusible low molecular weight species of RNA. After 30-min pulses, activity was exclusively associated with pancreatic RNase-sensitive single-stranded RNA. After 60-min labeling, tritium from uridine-5-H3 was taken up into nuclear DNA in addition to RNA.