Polymerase Synthesis of Photocaged DNA Resistant against Cleavage by Restriction Endonucleases

5-[(2-Nitrobenzyl)oxymethyl]-2′-deoxyuridine 5′-O-triphosphate was used for polymerase (primer extension or PCR) synthesis of photocaged DNA that is resistant to the cleavage by restriction endonucleases. Photodeprotection of the caged DNA released 5-hydroxymethyluracil-modified nucleic acids, which were fully recognized and cleaved by restriction enzymes.