Isolation and characterization of novel adenovirus type 12 E1A mRNAs by cDNA PCR technique.

The technique of cDNA polymerase chain reaction was used to study the heterogeneity of adenovirus type 12 early region 1A mRNAs in infected and transformed cells. In addition to 13 S and 12 S mRNAs, three transcripts of 10 S, 9.5 S, and 9 S could be isolated from infected HeLa cells. A fourth transcript of 11 S was found in transformed cells. The 9 S mRNA is generated by removing one intron (nucleotide (nt) 589 to nt 1143) from the RNA precursor. For the 11 S and 10 S mRNAs the primary transcript is spliced twice. The first splicing event removes a common intron from nt 589 to nt 715; the second splicing event removes introns deleted also during the processing of either the 13 S mRNA (leading to the 11 S mRNA) or the 12 S mRNA (leading to the 10 S mRNA). The 9.5 S mRNA is also generated by removing two introns (first splice junction: nt 588/852; the second splice junction is identical to that of the 12 S mRNA). In comparison to the 13 S and 12 S transcripts, the four smaller mRNAs alter the translational reading frames with the beginning of their second exons. In vitro translation of these mRNAs resulted in protein products with molecular weights of 10,100 (11 S and 10 S mRNAs), 10,500 (9.5 S mRNA), and 6200 (9 S mRNA) kDa.