Replication bypass of γ-HOPdG, reduced γ-HOPdG, and DNA–peptide cross-links by E. coli pol IV. Upper panel: Primer extensions by pol IV were carried out for 20 min in the presence of 100 µM dNTPs at 1.25 nM (lanes 3, 7, 11, 15, and 19), 2.5 nM (lanes 4, 8, 12, 16, and 20) or 5 nM (lanes 5, 9, 13, 17, and 21) protein concentrations. Lower panel: Single nucleotide incorporations by pol IV (1 nM) were carried out for 20 min in the presence of 20 µM individual dNTPs. M – oligodeoxynucleotide sizing markers; ND – non-damaged template; XL – cross-link-containing template.