Figure 2.

Structures of FAB-dUTP analogs and synthesis of photoreactive DNA₃. (A) Structures of three FAB-dUTP analogs. (B) Schematic representation of photoreactive DNA₃ synthesis in situ. The synthetic abasic site (X) in DNA₁ is incised by APE; DNA polymerase of the MEF extract incorporates dCMP, [α-³²P]dGMP or one of the photoreactive dUMP analogs (FAB-4-dUMP, FAB-4-ddUMP or FAB-9-dUMP) into the DNA. DNA₃ is ³²P-radiolabeled by incorporating dGMP (asterisk) and contained a 3′-end photoreactive dUMP (dU^R) residue.