A technique for identification of DNA-binding proteins and regions of DNA that bind proteins which combines aspects of Southern and western blotting techniques. A nuclear extract is separated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, renatured and blotted on to nitrocellulose, then exposed to labelled DNA probes. Photographic film laid against the gel is exposed so as to identify which protein bands have bound DNA probes, and then the DNA is extracted from them.