Transcripts of the adenovirus-associated virus genome: multiple polyadenylated RNAs including a potential primary...

Adenovirus-associated virus type 2 synthesizes four prominent viral transcripts, containing 4.3, 3.6, 2.6, and 2.3 kilobases (kb), in productively infected human KB cells (coinfected with adenovirus type 2). All species are polyadenylated and present in both nuclear and whole-cell RNA preparations, but only the predominant 2.3-kb (and possibly the 2.6-kb) RNA species are found on polysomes. Electrophoretic analyses under denaturing conditions of S1 nuclease-generated and exonuclease VII-generated DNA-RNA hybrids revealed, in each case, four protected DNA fragments which are equal in length (within 50 to 100 nucleotides) to the four S1 nuclease-generated hybrids resolved by electrophoresis under nondenaturing conditions. These results suggest that in the infected cell, abundant adenovirus-associated virus type 2 transcripts are present predominantly (by mass) as unspliced RNAs or, alternatively, they are spliced but contain very short (less than or equal to 50 nucleotides) leader sequences. That the 2.3-kb RNA represents such a spliced transcript is suggested by exonuclease VII mapping experiments and our more detailed RNA mapping studies (M. R. Green and R. G. Roeder, J. Virol., in press).