A HOTSPOT FOR PROMOTER-DEPENDENT RECOMBINATION IN POLYOMAVIRUS DNA

We have engineered polyomavirus (Py) DNA molecules carrying two large direct repeats within the late coding region, as well as a deletion en compassing the TATA box in the early promoter. Such constructs recombi ne less readily than a construct containing the same duplication of la te sequences, but an intact early promoter. Furthermore, residual reco mbination in the molecules with a deletion occurs between homologous s ites which differ from those used in the molecule without deletion. Th ese findings are consistent with recombination being stimulated by tra nscription originating from the early promoter, rather than facilitate d by the ''openness'' of viral chromatin undergoing transcription.