Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba, 278-8510, Japan.
Genes Cells. 2012 Sep;17(9):790-806. doi: 10.1111/j.1365-2443.2012.01628.x. Epub 2012 Aug 16.
DNA polymerase μ (pol μ) catalyzes nonhomologous end-joining in DNA double-stranded break repair. Pol μ consists of an amino-terminal BRCA1 carboxyl-terminal homology (BRCT) domain and a pol β-like region, which contains the catalytic site. By DNA cellulose column chromatography, using full-length pol μ and five different deletion mutants, we found that the amino-terminal region has double-stranded DNA (dsDNA)-binding activity. Pol μ without BRCT domain reduces the DNA polymerization activity when compared to full-length pol μ. Observation by atomic force microscopy showed that full-length pol μ binds to the ends and middle part of dsDNA. Pol μ lacking the amino-terminal region or with a mutation within the BRCT domain bound only to DNA ends, whereas the amino-terminal region with the BRCT domain bound to both the ends and the middle part of dsDNA (mpdDNA). Terminal deoxynucleotidyltransferase, which, like pol μ, belongs to the X family DNA polymerases, also bound to mpdDNA through its amino-terminal region.
DNA 聚合酶 μ（pol μ）催化 DNA 双链断裂修复中的非同源末端连接。Pol μ 由氨基端 BRCA1 羧基末端同源（BRCT）结构域和 pol β 样结构域组成，其中包含催化位点。通过 DNA 纤维素柱层析，使用全长 pol μ 和五个不同的缺失突变体，我们发现氨基端区域具有双链 DNA（dsDNA）结合活性。与全长 pol μ 相比，没有 BRCT 结构域的 pol μ 降低了 DNA 聚合酶活性。原子力显微镜观察显示，全长 pol μ 结合到 dsDNA 的末端和中间部分。缺乏氨基端区域或 BRCT 结构域内发生突变的 pol μ 仅与 DNA 末端结合，而带有 BRCT 结构域的氨基端区域则与 dsDNA 的末端和中间部分结合（mpdDNA）。末端脱氧核苷酸转移酶与 pol μ 一样属于 X 家族 DNA 聚合酶，也通过其氨基端区域与 mpdDNA 结合。
