Shiraishi Miyako, Ishino Sonoko, Yamagami Takeshi, Egashira Yuriko, Kiyonari Shinichi, Ishino Yoshizumi
Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, Fukuoka 812-8581, Japan.
Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, Fukuoka 812-8581, Japan
Nucleic Acids Res. 2015 Mar 11;43(5):2853-63. doi: 10.1093/nar/gkv121. Epub 2015 Feb 18.
DNA is constantly damaged by endogenous and environmental influences. Deaminated adenine (hypoxanthine) tends to pair with cytosine and leads to the A:T→G:C transition mutation during DNA replication. Endonuclease V (EndoV) hydrolyzes the second phosphodiester bond 3' from deoxyinosine in the DNA strand, and was considered to be responsible for hypoxanthine excision repair. However, the downstream pathway after EndoV cleavage remained unclear. The activity to cleave the phosphodiester bond 5' from deoxyinosine was detected in a Pyrococcus furiosus cell extract. The protein encoded by PF1551, obtained from the mass spectrometry analysis of the purified fraction, exhibited the corresponding cleavage activity. A putative homolog from Thermococcus kodakarensis (TK0887) showed the same activity. Further biochemical analyses revealed that the purified PF1551 and TK0887 proteins recognize uracil, xanthine and the AP site, in addition to hypoxanthine. We named this endonuclease Endonuclease Q (EndoQ), as it may be involved in damaged base repair in the Thermococcals of Archaea.
DNA 不断受到内源性和环境因素的损伤。脱氨基腺嘌呤（次黄嘌呤）倾向于与胞嘧啶配对，并在 DNA 复制过程中导致 A:T→G:C 转换突变。核酸内切酶 V（EndoV）水解 DNA 链中脱氧次黄苷 3' 端的第二个磷酸二酯键，被认为负责次黄嘌呤切除修复。然而，EndoV 切割后的下游途径仍不清楚。在嗜热栖热菌细胞提取物中检测到从脱氧次黄苷 5' 端切割磷酸二酯键的活性。从纯化组分的质谱分析中获得的由 PF1551 编码的蛋白质表现出相应的切割活性。来自柯达嗜热栖热菌的推定同源物（TK0887）表现出相同的活性。进一步的生化分析表明，纯化的 PF1551 和 TK0887 蛋白除了识别次黄嘌呤外，还识别尿嘧啶、黄嘌呤和 AP 位点。我们将这种核酸内切酶命名为核酸内切酶 Q（EndoQ），因为它可能参与古菌嗜热栖热菌属中的损伤碱基修复。
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