Simian virus 40 early mRNA's. I. Genomic localization of 3' and 5' termini and two major splices in mRNA from transformed and lytically infected cells.
We have studied the structure of polyadenylated virus-specific cytoplasmic mRNA's in mouse and human cells transformed by simian virus 40 and in monkey cells infected with simian virus 40 in the presence of cytosine arabinoside by means of reverse transcriptase-catalyzed complementary DNA synthesis and complementary DNA sequencing. Abundant mRNA species containing splices from residues 4490 to 4557 (0.533 to 0.546 map units [m.u.]) and 4490 to 4837 (0.533 to 0.600 m.u.) were identified in both transformed and infected cells. Two principal reverse transcriptase stops were observed at the 5' termini of these mRNA's, both occurring with approximately equal frequency. The most distal of these stops was localized at residues 5152 to 5154 (0.660 m.u.), and the second was at residues 5147 to 5148 (0.659 m.u.). Several additional minor stops, between approximately 0.62 and 0.65 m.u., were also found on complementary DNA copied from transformed cell mRNA; in contrast, only one additional stop was present on complementary DNA copied from early lytic mRNA. These data suggest the presence of a prinicipal 5' terminus of early lytic and transformed cell mRNA's at residues 5152 to 5154 and raise the possibility of additional 5' termini at one or more locations in the 0.62 to 0.659 m.u. region of these mRNA's. Transformed cell mRNA was also found to contain a single 3' terminus at positions 2504 and 2505 (0.153 m.u.); termini lying beyond this site were not detected.