title: Sequence-dependent variability of DNA structure. Influence of flanking sequences and fragment length on digestion by conformationally sensitive nucleases.
abstract: DNase I and 1,10-phenanthroline-copper are two nucleolytic activities which are sequence-dependent in their scission reaction yet are not nucleotide-specific at their site of cutting. When these two nucleases are used to digest identical sequences in 18-base pair oligonucleotides and in restriction fragments 10-fold longer, the digestion patterns are similar at sequence positions in the interior of the fragment. Changes in reactivity to 1,10-phenanthroline-copper associated with mutational changes in the lac promoter in biochemically functional restriction fragments are duplicated in 18-base pair oligonucleotides. The structural variability of a given DNA sequence detected by these conformationally sensitive nucleolytic activities is therefore encoded in local sequence and not sensitive to fragment length. Digestion patterns of a repeated 7-base pair sequence within a longer sequence have the same characteristic except for the two nucleotides at the 5' periphery of the direct repeat. This conclusion is based on the digestion pattern of a restriction fragment which contains the polyadenylation site of the mouse immunoglobulin mu heavy chain gene. Two pairs of different 7-base pair sequences repeated in this fragment retain their distinctive digestion patterns. DNA sequences which comprise the binding sites of regulatory proteins, retain a characteristic structure only influenced at their peripheries by two to three bases of the flanking sequence.
mesh_terms: D004247:DNA / Q000032:analysis*; D003850:Deoxyribonuclease I / Q000378:metabolism; D007148:Immunoglobulin mu-Chains / Q000235:genetics; D007763:Lac Operon; D009690:Nucleic Acid Conformation; D010618:Phenanthrolines
chemical_list: D007148:Immunoglobulin mu-Chains; D010618:Phenanthrolines; D004247:DNA; D003850:Deoxyribonuclease I; C025205:1,10-phenanthroline