Illegitimate recombination in a bovine papillomavirus shuttle vector: a high level of site specificity.

Recombination in a bovine papillomavirus shuttle vector carrying direct repeats of Moloney murine leukemia virus LTR sequence was examined. Differently from similar vectors carrying direct repeats of SV40 polyA addition signal or neomycin resistance gene, the vector exhibited no homologous recombination between the repeats. Instead, illegitimate recombination took place. There were two major types of recombination products from the restriction cleavage pattern. The plasmids in independent cellular clones belonging to the same recombination type shared the identical crossover point. Thus, in this plasmid, illegitimate recombination occurred at preferential sites involving exactly the same sequences.