Sensitivity of superhelical DNA to a single-strand specific endonuclease.

摘要: Abstract Superhelical and non-superhelical closed circular replicative form DNAs of bacteriophage ΦX174 were incubated with various concentrations Neurospora crassa endonuclease, an enzyme highly specific for single-stranded nucleic acids. The superhelical DNA was found to be more sensitive the endonuclease than duplex. duplex reacted formaldehyde in temperature range 22–60 °C any regions fixed by hydroxymethylation cleaved using at a concentration 2 units/ml—a without effect on non-formaldehyde-treated molecules. These experiments indicated that, under conditions used, region accessible fixation existed molecule temperatures as low 22 °C; contrast, some 20 higher required during reaction obtain comparable sensitization enzyme. Only one “endonuclease-sensitive” appears present each molecule.