PROCESSING OF LATE ADENOVIRUS NUCLEAR-RNA TO MESSENGER-RNA - KINETICS OF FORMATION OF INTERMEDIATES AND DEMONSTRATION THAT ALL EVENTS ARE NUCLEAR

Expression of the major late adenovirus transcription unit (which maps between co-ordinates 16 and 99 on the genome) results in the production of five distinct poly(A)-containing RNAs, which are the initial precursors to one of five 3′ coterminal mRNA groups. These initial precursors are processed with a half-life of approximately 30 minutes after the initial poly(A) addition step, which occurs within one to two minutes after transcription of sequences at the poly(A) addition site. The nuclear precursor molecules that eventually yield the fiber mRNA were examined in detail. Four distinct nuclear poly(A)-containing RNAs with 3′ termini at 91·5 were detected. The largest species represents an unspliced molecule and the smallest is the size of the mature mRNA. The two intermediatesized species presumably represent partially spliced molecules. In addition, a precursor product relationship between the species was indicated by kinetic analyses. Finally, it would appear that all major processing steps occur in the nucleus. In the case of the mRNA group that has a 3′ terminus at 51·0, all of the mRNA species of the group were detected in mRNA that had just appeared in the cytoplasm and in approximately the same molar ratios as in samples labeled for longer. © 1979.