DNA-BINDING OF THE BORDETELLA-PERTUSSIS H1 HOMOLOG ALTERS IN-VITRO DNA FLEXIBILITY

BpH1, the Bordetella pertussis H1 homolog, interacts with chromosomal DNA. With DNase I protection assays, we demonstrate in this study that BpH1 hinds DNA in a nonspecific manner and that it may cover DNA frag ments from end to end, Although the binding was shown to he nonspecifi c, preferential binding sites and sites resistant to BpH1 binding were identified within and upstream of the pertussis toxin promoter sequen ce, In the presence of DNA ligase, BpH1 favored the formation of multi meric DNA fragments of various sizes and prevented ring closures, sugg esting a diminished flexibility of the DNA fragments and thus indicati ng that BpH1 acts as a macromolecular crowding agent.