Site-specific DNA cleavage by Cu(II) complexes of podophyllotoxin derivatives.

Site-specific DNA cleavage in the presence of Cu(II) complexes of podophyllotoxin derivatives was investigated with a modified Sanger sequencing method. Cu(II) complexes of 4'-demethylepipodophyllotoxin (DEPD) and syringic acid (SA) cleaved M13mp18 single-strand DNA site-specifically at both cytosine (C) and guanine (G) positions in the GC rich regions and C position, respectively, at pH 7.8. The apparent binding constants of calf thymus DNA-Cu(II) complexes estimated by the differential UV-absorption spectra revealed that both Cu(II)-VP-16 and -DEPD complexes bind to DNA more strongly than does the Cu(II)-SA complex.