DNA-REPAIR RATES MAPPED ALONG THE HUMAN PGK1 GENE AT NUCLEOTIDE RESOLUTION

The repair of cyclobutane pyrimidine dimers (CPDs), DNA lesions induce d by ultraviolet light, was studied at nucleotide resolution. Human fi broblasts were irradiated with ultraviolet light and allowed to repair . The DNA was enzymatically cleaved at the CPDs, and the induced break s along the promoter and exon 1 of the PGK1 gene were mapped by ligati on-mediated polymerase chain reaction. Repair rates within the nontran scribed strand varied as much as 15-fold, depending on nucleotide posi tion. Preferential repair of the transcribed strand began just downstr eam of the transcription start site but was most pronounced beginning at nucleotide +140 in exon 1. The promoter contained two slowly repair ed regions that coincided with two transcription factor binding sites.