Polymerase μ in non-homologous DNA end joining: importance of the order of arrival at a double-strand break in a purified system.

ABSTRACT: During non-homologous DNA end joining (NHEJ), bringing two broken dsDNA ends into proximity is an essential prerequisite for ligation by XRCC4:Ligase IV (X4L4). This physical juxtaposition of DNA ends is called NHEJ synapsis. In addition to the key NHEJ synapsis proteins, Ku, X4L4, and XLF, it has been suggested that DNA polymerase mu (pol μ) may also align two dsDNA ends into close proximity for synthesis. Here, we directly observe the NHEJ synapsis by pol μ using a single molecule FRET (smFRET) assay where we can measure the duration of the synapsis. The results show that pol μ alone can mediate efficient NHEJ synapsis of 3' overhangs that have at least 1 nt microhomology. The abundant Ku protein in cells limits the accessibility of pol μ to DNA ends with overhangs. But X4L4 can largely

SUBMITTER: Zhao B 

PROVIDER: S-EPMC7144918 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature