A binding protein (p82 protein) recognizes specifically the curved heterochromatic DNA in Artemia franciscana

DNA bending has been suggested to play a role in the regulation of gene expression, initiation of DNA replication, site specific recombination and DNA packaging. In Artemia franciscana (Phillopoda anostraca) cells we have revealed that an AluI DNA family of repeats, 113-bp in length, is the major component of the constitutive heterochromatin found in the species. By analysis of cloned oligomeric (monomer to hexamer) heterochromatic fragments and electrophoretic experiments we verified that the repetitive DNA shows a stable curvature that confers a solenoidal geometry to the double helix. Using the cloned monomeric fragment, as molecular probe, we describe the detection in an A. franciscana cell extract of a protein of 82 kDa (p82) that preferentially binds to heterochromatic DNA. This protein, purified of the other DNA binding proteins present in the crude cell extract, shows a greater affinity with the tandem copies of the AluI DNA fragment than with the monomer sequence. The binding of p82 protein to heterochromatic DNA is also drastically reduced in the presence of the antibiotic distamycin A, suggesting a role of the DNA curvature in the formation of the nucleoproteic complex.