Improved Plasmid Vectors for the Analysis of Protein-Induced DNA Bending

Bending of DNA by proteins plays an important role in transcription initiation, DNA replication, and recombination. The degree of pro- tein-induced DNA bending is conveniently determined by combin- ing gel retardation techniques with the use of so-called bending vectors (1 ,2 ). Bending vectors contain duplicated circular permuted restric- tion sites and cloning sites for insertion of protein binding sequences. Restriction enzyme digestion readily generates fragments that are identical in size, but differ in the location of the binding site (Fig. 1 ).