Tan Jun, Wang Xiangyu, Hwang Bor-Jang, Gonzales Rex, Konen Olivia, Lan Li, Lu A-Lien
Massachusetts General Hospital Cancer Center, Department of Radiation Oncology, Harvard Medical School, Charlestown, MA 02129, USA.
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
Aging (Albany NY). 2020 Sep 29;12(18):17761-17785. doi: 10.18632/aging.103934.
In the base excision repair pathway, MYH/MUTYH DNA glycosylase prevents mutations by removing adenine mispaired with 8-oxoG, a frequent oxidative lesion. MYH glycosylase activity is enhanced by Rad9-Rad1-Hus1 (9-1-1) checkpoint clamp and SIRT6 histone/protein deacetylase. Here, we show that MYH, SIRT6, and 9-1-1 are recruited to confined oxidatively damaged regions on telomeres in mammalian cells. Using different knockout cells, we show that SIRT6 responds to damaged telomeres very early, and then recruits MYH and Hus1 following oxidative stress. However, the recruitment of Hus1 to damaged telomeres is partially dependent on SIRT6. The catalytic activities of SIRT6 are not important for SIRT6 response but are essential for MYH recruitment to damaged telomeres. Compared to wild-type MYH, the recruitment of hMYH mutant (defective in both SIRT6 and Hus1 interactions), but not hMYH mutant (defective in Hus1 interaction only), to damaged telomeres is severely reduced. The formation of MYH/SIRT6/9-1-1 complex is of biological significance as interrupting their interactions can increase cell's sensitivity to HO and/or elevate cellular 8-oxoG levels after HO treatment. Our results establish that SIRT6 acts as an early sensor of BER enzymes and both SIRT6 and 9-1-1 serve critical roles in DNA repair to maintain telomere integrity.
在碱基切除修复途径中，MYH/MUTYH DNA糖基化酶通过去除与8-氧代鸟嘌呤错配的腺嘌呤来防止突变，8-氧代鸟嘌呤是一种常见的氧化性损伤。Rad9-Rad1-Hus1（9-1-1）检查点钳和SIRT6组蛋白/蛋白质去乙酰化酶可增强MYH糖基化酶活性。在此，我们表明，MYH、SIRT6和9-1-1被招募到哺乳动物细胞端粒上受限的氧化损伤区域。使用不同的基因敲除细胞，我们发现SIRT6对受损端粒的反应非常早，然后在氧化应激后招募MYH和Hus1。然而，Hus1被招募到受损端粒部分依赖于SIRT6。SIRT6的催化活性对SIRT6的反应并不重要，但对MYH被招募到受损端粒至关重要。与野生型MYH相比，hMYH突变体（在与SIRT6和Hus1的相互作用中均有缺陷）而非hMYH突变体（仅在与Hus1的相互作用中有缺陷）被招募到受损端粒的能力严重降低。MYH/SIRT6/9-1-1复合物的形成具有生物学意义，因为中断它们之间的相互作用会增加细胞对羟基脲（HU）的敏感性和/或在HU处理后提高细胞内8-氧代鸟嘌呤水平。我们的结果表明，SIRT6作为碱基切除修复酶的早期传感器，SIRT6和9-1-1在维持端粒完整性的DNA修复中都起着关键作用。
