Conservation of DNA bend sites with identical superhelical twists among the human, mouse, bovine, rabbit and chicken beta-globin genes

We reported previously that DNA bend sites appear in the human beta-globin locus at an average distance of 680 bp. The relative locations of the sites were conserved among the five active beta-like globin genes and one pseudo gene. Here, we mapped the sites in the beta-like globin genes from various species and examined their conservation. The locations of the bend sites in the bovine, rabbit and chicken beta-globin genes mapped here showed marked conservation in their locations relative to the cap site and showed simila r locations to the previously mapped sites in the human beta- and mouse bet a(maj)-globin genes. Further analysis of the first bend sites from the cap site (B-1 sites) indicated that they contained tracts of adenines and thymi nes longer than or equal to two bases. This sequence feature contributed mo stly to the curvature profiles revealed by gel assays and/or by computer-ba sed TRIF analysis. TRIF analysis indicated that most of the B-1 sites showe d right-handed superhelical twists accompanied by left handed twists. This was confirmed by the effect of ethidium bromide on the superhelical twists in the assays.