Figure 6.

Mapping of UV-induced DNA damage in the cII transgene in mouse genomic DNA irradiated with various UV wavelengths. TD-PCR footprinting of the full-length cII transgene was done using genomic DNA of mouse embryonic fibroblasts irradiated with a series of UV wavelengths (λ=261–349 nm) at a constant dose of 0.5 J/cm² in comparison with control, as described in Materials and Methods. In addition to the IRDye 700 Sizing Standard (LI-COR), Maxam and Gilbert chemical reactions, prepared from control genomic DNA and subjected to ligation-mediated PCR (LM-PCR; ref. 50), were run in parallel to all samples (last 4 lanes: G, G/A, C, C/T). This strategy will help locate the exact position of each base along the reference DNA sequence. LM-PCR bands migrate ∼3 bases faster than the corresponding TD-PCR bands due to the addition of 3 riboguanosine triphosphates to all primer extension products in the latter method (31, 48). M, molecular size marker.