The effect of bisulfite modification on the template activity of DNA for DNA polymerase I.

Cytosine residues of poly(C) and heat-denatured calf thymus DNA were transformed into 5,6-dihydrouracil-6-sulfonate (U(SO(-) (3))) residues by treatment with bisulfite. The poly(U(SO(-) (3))(2), C(3)) and poly(U(SO(-) (3))(9), C(1)) prepared did not form inter-base binding with either poly(A) or poly(I) as judged by the absence of hypochromicity in ultraviolet absorbance. U(SO(-) (3)) residues in the DNA inactivated it to serve as template for E.coli DNA polymerase I, while the template activity was restored by conversion of the U(SO(-) (3)) residues into U.