The mechanism of DNA repair by uracil-DNA glycosylase: Studies using nucleotide analogues

2',4'-Dideoxy-4'-methyleneuridine incorporated into oligodeoxynucleotides f orms regular B-DNA duplexes as shown by T-m and CD measurements. Such oligo mers are not cleaved by the DNA repair enzyme, UDG, which cleaves the glyco sylic bond in dU but not in dT nor in dC nucleosides in single stranded and double stranded DNA. Differential binding of oligomers containing carbadU, 4'-thiodU, and dU residues to wild type and mutant UDG proteins identify a n essential role for the furanose 4'-oxygen in recognition and cleavage of dU residues in DNA.