Figure 8.

Model for TCR in mammalian cells. For simplicity we show a gene with four RNAPIIs in poised state at the 5′ region of the gene and three CPDs in the transcribed strand. After each RNAPII-CPD encounter, the damage is repaired, and the RNAPII behind continues transcription until it encounters the next CPD, resulting in repair and dissociation of RNAPII and continuation of repair by the following RNAPIIs until the track is completely cleared of damage. In our experiments, the DRB2 (pulse–chase–pulse) regimen permitted only limited release of RNAPII during the 10-min DRB-free chase period, allowing repair of only the initial damage site at the 5′ end of the gene.