THE USE OF CHROMATOGRAPHY ON BENZOYL-NAPHTHYL-DEAE-CELLULOSE TO DETERMINE THE ABILITY OF PROTEINS FROM EHRLICH ASCITES-CARCINOMA, WHICH BIND TO SINGLE-STRANDED-DNA (SSB-PROTEINS), TO DESTABILIZE THE DNA DOUBLE HELIX

SSB-Proteins from Ehrlich ascites carcinoma (EAC) were incubated for 30 min in the presence of 5 mM NaCl with salmon sperm DNA or [H-3]DNA from EAC (weight ratios of SSB-proteins/DNA from 0 to 4.5), SDS was added to a 0.05% concentration, and the mixture was applied to columns with benzoyl-naphthyl-DEAE-cellulose. Double-stranded DNA was eluted by 1 M NaCl, and the DNA containing single-stranded regions with eluted by 50% dimethylformamide. With increasing weight ratio SSB-protein/DNA, a progressive decrease in the DNA content in the first eluate and an increase in the second were detected. The effect is more pronounced when homologous DNA is used and is not associated with nuclease activity of the SSB-proteins. It is concluded that the SSB-proteins from EAC are "DNA-unwinding proteins."