Action of pancreatic DNase: requirements for activation of DNA as a template-primer for DNA polymerase ∝

Abstract

Pancreatic DNase requires both Ca ²⁺ and Mg ²⁺ for its activity as measured by formation of an activated DNA template for in vitro DNA polymerase α assay and by the hyperchromic shift. Mn ²⁺ can partially satisfy the Mg ²⁺ requirement of the DNase for activation of DNA but the resulting template is only 50% as active in the DNA polymerase assay. When precautions are taken to avoid divalent ion contamination, pancreatic DNase is not active in the presence of Ca ²⁺ or Mg ²⁺ alone. Analysis of the DNA by sucrose gradient centrifugation shows that only in the presence of Ca ²⁺ plus Mg ²⁺ or Mn ²⁺ does pancreatic DNase produce extensive strand breaks in the DNA. The activated DNA template that yields maximal DNA polymerase activity is low molecular weight material of 30,000 to 50,000 daltons.