Proof of recombination between viral and cellular genomes in human KB cells productively infected by adenovirus type 12: structure of the junction site in a symmetric recombinant (SYREC).

In previous work we have described a symmetric recombinant (SYREC1) between Ad12 DNA and human KB cell DNA. This recombinant DNA molecule has been generated during productive infection and is encapsidated into virions. From the DNA of a similar symmetric recombinant (termed SYREC2) between the left terminus of Ad12 DNA and human KB cellular DNA, the site of linkage between the two DNAs was cloned and sequenced. It was demonstrated that the first 2081 Ad12 nucleotides counting from the left viral terminus are conserved and linked to a sequence of GC-rich (70.4% G + C) KB cell DNA which occurs about 20 times per cellular genome. Except for a common 5'-CTGGC-3' pentanucleotide between the Ad12 DNA and KB cell DNA sequences, extensive patch homologies were not apparent at the site of junction. Similarly, comparisons of the deleted Ad12 DNA sequence and the cellular sequence replacing it did not reveal patch homologies. The 304 bp abutting the Ad12 terminus were shown to hybridize to KB cell DNA. These results provided definitive proof for the occurrence of recombinants between viral and cellular DNAs in human cells productively infected by Ad12 as previously shown by less direct experiments (Burger and Doerfler, 1974; Schick et al., 1976). Across the site of junction, an open reading frame exists which extends the truncated 54-kDal protein of the E1b region of Ad12 DNA for another 66 amino acids encoded by KB cellular DNA. This sequence is terminated by two UGA translational termination signals. The hypothetical protein has not yet been isolated.