Abstract
During productive infection of human cells, adenovirus serotype 2 transcription proceeds through early and late stages of transcription, which are separated by the onset of DNA replication. In this paper we analyze the 3′-terminal sequences of messenger RNAs from five early transcription units, and messenger RNA from the L2, L3 and L4 families of the major late transcription unit. By correlating RNAase T 1 oligonucleotides near poly(A) with the DNA sequence of Ad-2 ∥ ∥ Abbreviation used: Ad-2, adenovirus serotype 2. we have defined the poly(A) acceptor sequences of these messengers. Our principal conclusions are as follows. 1. (1)The A-A-U-A-A-A hexanucleotide homology common to many cellular mRNA 3′ ends is present near poly(A) of all but one of the mRNAs studied. Notably, it is present within the major late transcription unit at the L2, L3 and L4 coterminal family poly(A) sites, and potentially at all five poly(A) sites of the late transcription unit. Because the latter mRNA 3′ ends are formed by cleavage, the hexanucleotide probably does not specify a RNA polymerase II termination site. 2. (2) An early region III poly(A) site apparently lacks the A-A-U-A-A-A homology and may be an exception to the above generalizations. 3. (3) Region EIb and protein IX mRNA share a common poly(A) site, although their precursors are initiated at separate promoters. Also, the same poly(A) sites at the left end function during the early and late stages of infection. Thus, these poly(A) sites are not regulated in a stage-specific manner, and may function for precursors initiated at more than one promoter. 4. (4) Residues near poly(A) of mRNA belonging to the 3′ coterminal families of the late transcription unit form ribonuclease-resistant hybrids to Ad-2 DNA which encode mRNA main body sequences. Thus late mRNA 3′ ends are locally encoded. We present a model for sequence recognition during formation of 3′ ends, and discuss autonomy of poly(A) site function.
Published Version
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