Modes of termination of DNA polymerases at DNA–protein cross-links in the displaced strand of double-stranded DNA.

<p>(A) Scheme of the DPC substrate. (B) Synthesis with processive strand displacement with a stop before the cross-link site: <i>Taq</i> DNA polymerase (Family A). (C) Synthesis with hit-and-run strand displacement with a stop before the cross-link site: human DNA polymerase β (Family X). <i>Lanes 1–3</i>, size markers corresponding to the primer (<i>lane 1</i>, 11 nt long), full-size product (<i>lane 2</i>, 40 nt), and primer extended to the cross-link site (<i>lane 3</i>, 23 nt). <i>Lane 4</i>, the substrate in the absence of DNA polymerase, <i>lanes 5–9</i>, extension by the DNA polymerase for the indicated time. In <i>lane 8</i>, the reaction was carried out with a primer–template substrate, and in <i>lane 9</i>, with a primer–undamaged downstream strand–template substrate.