Direct preparation of sticky-ended duplexes within PCR by using caged primers

Control of the terminal structures of PCR products is crucially important to facilitate molecular biology and biotechnology. Here, we report a new method to prepare PCR products having desired sticky ends directly after thermal cycles. When a pair of caged primers is used, polymerase reaction is site-selectively terminated in front of the caged nucleotide, and the 5'- portion of the primer remains single-stranded throughout the reaction. Successive removal of the photo-cleavable protecting group gives restriction-enzyme free sticky ends on the product. We succeeded in applying this technique to make a recombinant vector bearing GFP gene.