Department of Biochemistry & Molecular Biology, Indiana University Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Biochemistry. 2011 May 24;50(20):4360-70. doi: 10.1021/bi200333k. Epub 2011 Apr 27.
Metnase (SETMAR) is a SET-transposase fusion protein that promotes nonhomologous end joining (NHEJ) repair in humans. Although both SET and the transposase domains were necessary for its function in DSB repair, it is not clear what specific role Metnase plays in the NHEJ. In this study, we show that Metnase possesses a unique endonuclease activity that preferentially acts on ssDNA and ssDNA-overhang of a partial duplex DNA. Cell extracts lacking Metnase poorly supported DNA end joining, and addition of wt-Metnase to cell extracts lacking Metnase markedly stimulated DNA end joining, while a mutant (D483A) lacking endonuclease activity did not. Given that Metnase overexpression enhanced DNA end processing in vitro, our finding suggests a role for Metnase's endonuclease activity in promoting the joining of noncompatible ends.
Metnase（SETMAR）是一种 SET 转座酶融合蛋白，可促进人类的非同源末端连接（NHEJ）修复。虽然 SET 和转座酶结构域对于 DSB 修复中的功能都是必需的，但 Metnase 在 NHEJ 中具体发挥什么作用尚不清楚。在这项研究中，我们表明 Metnase 具有独特的内切酶活性，该活性优先作用于 ssDNA 和部分双链 DNA 的 ssDNA 突出端。缺乏 Metnase 的细胞提取物对 DNA 末端连接的支持能力很差，而向缺乏 Metnase 的细胞提取物中添加 wt-Metnase 可显著刺激 DNA 末端连接，而缺乏内切酶活性的突变体（D483A）则不能。鉴于 Metnase 的过表达增强了体外 DNA 末端加工，我们的发现表明 Metnase 的内切酶活性在促进不兼容末端的连接中起作用。
