PMID: 32963245

Authors:

Kaminski AM, Pryor JM, Ramsden DA, Kunkel TA, Pedersen LC, Bebenek K

Title:

Structural snapshots of human DNA polymerase mu engaged on a DNA double-strand break.

Journal:

Nat Commun. 2020 Sep 22;11(1):4784. doi: 10.1038/s41467-020-18506-5.

Abstract:

Genomic integrity is threatened by cytotoxic DNA double-strand breaks (DSBs), which must be resolved efficiently to prevent sequence loss, chromosomal rearrangements/translocations, or cell death. Polymerase mu (Polmu) participates in DSB repair via the nonhomologous end-joining (NHEJ) pathway, by filling small sequence gaps in broken ends to create substrates ultimately ligatable by DNA Ligase IV. Here we present structures of human Polmu engaging a DSB substrate. Synapsis is mediated solely by Polmu, facilitated by single-nucleotide homology at the break site, wherein both ends of the discontinuous template strand are stabilized by a hydrogen bonding network. The active site in the quaternary Pol mu complex is poised for catalysis and nucleotide incoporation proceeds in crystallo. These structures demonstrate that Polmu may address complementary DSB substrates during NHEJ in a manner indistinguishable from single-strand breaks.