(D) Incision/excision activity of combinations of altered TFIIH complexes in a reconstituted NER reaction. Equal amounts of single or mixed populations of recombinant TFIIHs (containing XPD, XPB, p62, p52, His-p44, Flag-p34, cdk7, cyclin H, Mat1, and p8) were mixed with recombinant XPG, XPF/ERCC1, XPC/hHR23B, RPA, and a radiolabelled synthetic NER substrate. The excision products (26–34 nucleotides in length) were visualised at nucleotide resolution on a denaturing polyacrylamide gel as indicated . Note the weak activity corresponding to each single and combined TFIIH complex (lanes 3–8) relative to the wt (lane 1) and negative controls (lane 2).