FIG. 5.

Repair of UV-induced CPDs (A) and 6-4PPs (B) along the URA3 template strand in a rad7 strain. Repair was monitored at 0, 20, 40, and 60 min after irradiation (70 J/m²). The large arrow indicates the major transcription-initiation site (+1) and the direction of transcription. To account for background levels, nonirradiated DNA was also assayed (indicated by a minus sign). Due to the lower induction frequency of 6-4PPs than of CPDs, twice the amount of DNA was assayed in the 6-4PP analysis and different exposure times were used to allow visual inspection. As calculated from short exposures of the undamaged full-length fragment (not indicated), the autoradiograms display a 3- to 3.5-fold amplification of the actual 6-4PP signal relative to that of the CPDs. The asterisk indicates a UV-independent background signal.