title: Poly(ADP-ribose) polymerase forms loops with DNA.
abstract: The interaction between highly purified poly(ADP-ribose) polymerase from calf thymus and different topological forms of pBR322 DNA has been studied by gel retardation electrophoresis and electron microscopy. We show that: (i) in the absence of nicks on DNA the enzyme has a marked affinity for supercoiled (form I) DNA, (ii) in the presence of single stranded breaks poly(ADP-ribose) polymerase preferentially binds to form II, (iii) in all cases enzyme molecules are frequently located at DNA intersections, (iv) a cooperative binding of the enzyme on DNA occurs.
mesh_terms: D004247:DNA / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004586:Electrophoresis; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D009690:Nucleic Acid Conformation; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D004278:DNA, Superhelical; D004268:DNA-Binding Proteins; D004247:DNA; D011065:Poly(ADP-ribose) Polymerases