PMID: 25775267

Authors:

Zahn KE, Averill AM, Aller P, Wood RD, Doublie S

Title:

Human DNA polymerase theta grasps the primer terminus to mediate DNA repair.

Journal:

Nat Struct Mol Biol. 2015 Mar 16. doi: 10.1038/nsmb.2993.

Abstract:

DNA polymerase theta protects against genomic instability via an alternative end-joining repair pathway for DNA double-strand breaks. Polymerase theta is overexpressed in breast, lung and oral cancers, and reduction of its activity in mammalian cells increases sensitivity to double-strand break-inducing agents, including ionizing radiation. Reported here are crystal structures of the C-terminal polymerase domain from human polymerase theta, illustrating two potential modes of dimerization. One structure depicts insertion of ddATP opposite an abasic-site analog during translesion DNA synthesis. The second structure describes a cognate ddGTP complex. Polymerase theta uses a specialized thumb subdomain to establish unique upstream contacts to the primer DNA strand, including an interaction with the 3'-terminal phosphate from one of five distinctive insertion loops. These observations demonstrate how polymerase theta grasps the primer to bypass DNA lesions or extend poorly annealed DNA termini to mediate end-joining.