Hairpin-shaped DNA duplexes with disulfide bonds in sugar-phosphate backbone as potential DNA reagents for crosslinking with proteins

Convenient approaches mere described to incorporate -OP(=O)O--SS-O-(O=)PO- bridges in hairpin-shaped DNA duplexes instead of regular phosphodiester li nkages: (i) H2O2- or 2,2'-dipyridyldisulfide-mediated coupling of 3'- and 5 '-thiophosphorylated oligonucleotides on complementary template and (ii) mo re selective template-guided autoligation of a preactivated oligonucleotide derivative with an oligomer carrying a terminal thiophosphoryl group. Dith iothreitol was found to cleave completely modified internucleotide linkage releasing starting oligonucleotides. The presence of complementary template as an intrinsic element of the molecule protects the hairpin DNA analog fr om spontaneous exchange of disulfide-linked oligomer fragments and makes it a good candidate for auto-crosslinking with cysteine-containing proteins. (C) 1999 Federation of European Biochemical Societies.