SPLICING PATTERNS OF NUCLEAR PRECURSORS TO THE MESSENGER-RNA FOR ADENOVIRUS 2 DNA BINDING-PROTEIN

The relationship of nuclear and cytoplasmic RNAs from early region 2 of the adenovirus 2 genome (map positions 61.6-75.0) has been determined. The 20S cytoplasmic mRNA which codes for the 72K DNA-binding protein has been shown to contain spliced sequences as previously reported (Berk and Sharp, 1977b; Kitchingman, Lai and Westphal, 1977). The nuclear poly(A)-containing RNA migrates as 28S, 23S and 20S molecules (Craig and Raskas, 1976). Structural analysis demonstrated that nuclear 23S and 20S RNAs lack intervening sequences (map positions 74.6-68.8) that are also absent from the cytoplasmic mRNA. In contrast, the nuclear 28S RNA has sequences complementary to the intervening DNA sequences. The analysis of colinear transcripts from the I strand of region 2 suggests that nuclear 28S and 23S RNAs contain the intervening sequences from a second splice (map positions 68.3-66.3). The nuclear 20S RNA, like the mature cytoplasmic mRNA, lacks these sequences. We also detected colinear polyadenylated transcripts from the r strand of region 2 that do not have any apparent relationship to early mRNA. In continuous label experiments, the 28S and 23S species reached a steady state within 30 min, whereas the amounts of nuclear and cytoplasmic 20S RNAs continued to increase for at least 3 hr. These studies suggest that the intervening DNA sequences of the 72K DNA binding protein gene are transcribed in its mRNA precursor (28S). These sequences are then removed sequentially to generate first a 23S intermediate and then a 20S nuclear RNA that will be transported to the cytoplasm as a mature mRNA. © 1979.