Gene and mRNA for precursor polypeptide VI from adenovirus type 2.

We present a 1,040-base-pair-long sequences of adenoviruses type 2 DNA which encodes the complete gene for precursor polypeptide VI (pVI). pVI consists of 250 amino acids amounting to a molecular weight of 26,990. The proteolytic cleavage maturing pVI to virion polypeptide VI removes 33 amino acids from the amino-terminal end of the polypeptide, thus giving the mature polypeptide VI a molecular weight of 23,400. The UAA stop codon terminating pVI translation is separated by 84 nucleotides from the initiator triplet for the hexon gene. Both polypeptides are encoded by the same translational reading frame, suggesting the evolution of pVI and hexon as separate proteins by the introduction of a termination codon and selection of a new splice acceptor site in an ancestral fused polypeptide chain. The splice site where the common tripartite leader is attached to the pVI mRNA precedes the initiator codon for pVI translation by one nucleotide and forms, together with other late splice acceptor sites, a late adenovirus consensus acceptor site. We also demonstrate that the 3' end of the mRNA's belonging to the L2 3'-cotermination family is located only 31 nucleotides upstream from the splice junction of the pVI mRNA. Furthermore, we show that four novel polypeptides of molecular weights 80,000, 39,000, 36,000, and 10,500 are encoded by region L2.