Hot spot for Tn1000 insertions in cloned repressor gene of the L phage

Insertions of Tn1000 into a cloned fragment of the L-phage genome comprising the repressor gene were prepared. Repressor activities produced by plasmids with insertions were assayed in vivo. As a result, the repressor gene was localized within 0.5 kb near one end of the cloned fragment. Transposon insertions were nonrandomly clustered within the repressor gene and in its close vicinity. An analysis of supercoiled plasmid DNA with the nuclease S1 revealed no distortion of the secondary structure of DNA in this region.