Characterization of the Single-Strand-Specific Nuclease S₁ Activity on Double-Stranded Supercoiled Polyoma DNA

Abstract

The DNA of polyoma virus consists of double-stranded supercoiled circular molecules. The single-strand-specific nuclease S₁ converts these molecules to unit length rods. The conversion occurs in a two-step reaction, with nuclease S₁ cutting first one of the two strands and then the intact strand opposite to this nick. Cleavage of intact polyoma DNA by nuclease S₁ is a consequence of supercoiling. DNA molecules containing random single-strand breaks introduced by physical or enzymatic means are also cut opposite to nicks.

Abbreviations

SV40

Simian virus 40

p.f.u.

plaque-forming units

Enzymes

 

(CBN Recommendations 1972). Aspergillus nuclease S₁ or single-stranded-nuclease endonuclease (EC 3.1.4.–)

 

pancreatic DNAase I or deoxyribonuclease I (EC 3.1.4.5)

 

RI restriction endonuclease (EC 3.1.4.-)