Effect of ERCC3 on promoter escape from premelted templates. Transcription reactions were performed by using the template −9/+2 in the presence of ATP and CTP (lanes 1–4), or ATP, CTP, UTP, and 3′-O-methyl GTP (lanes 5–8). The position of the initiation product (ApC) is indicated on the left, and the short transcripts are indicated on the right. WT, wild type.