Kusumoto-Matsuo Rika, Opresko Patricia L, Ramsden Dale, Tahara Hidetoshi, Bohr Vilhelm A
Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
Aging (Albany NY). 2010 May;2(5):274-84. doi: 10.18632/aging.100141.
Werner syndrome is an inherited human progeriod syndrome caused by mutations in the gene encoding the Werner Syndrome protein, WRN. It has both 3'-5' DNA helicase and exonuclease activities, and is suggested to have roles in many aspects of DNA metabolism, including DNA repair and telomere maintenance. The DNA-PK complex also functions in both DNA double strand break repair and telomere maintenance. Interaction between WRN and the DNA-PK complex has been reported in DNA double strand break repair, but their possible cooperation at telomeres has not been reported. This study analyzes thein vitro and in vivo interaction at the telomere between WRN and DNA-PKcs, the catalytic subunit of DNA-PK. The results show that DNA-PKcs selectively stimulates WRN helicase but not WRN exonuclease in vitro, affecting that WRN helicase unwinds and promotes the release of the full-length invading strand of a telomere D-loop model substrate. In addition, the length of telomeric G-tails decreases in DNA-PKcs knockdown cells, and this phenotype is reversed by overexpression of WRN helicase. These results suggest that WRN and DNA-PKcs may cooperatively prevent G-tail shortening in vivo.
沃纳综合征是一种遗传性人类早老综合征，由编码沃纳综合征蛋白（WRN）的基因突变引起。它具有3'-5' DNA解旋酶和核酸外切酶活性，被认为在DNA代谢的许多方面发挥作用，包括DNA修复和端粒维持。DNA-PK复合物也在DNA双链断裂修复和端粒维持中发挥作用。在DNA双链断裂修复中已报道WRN与DNA-PK复合物之间存在相互作用，但它们在端粒处可能的合作尚未见报道。本研究分析了WRN与DNA-PK的催化亚基DNA-PKcs在端粒处的体外和体内相互作用。结果表明，DNA-PKcs在体外选择性刺激WRN解旋酶而非WRN核酸外切酶，影响WRN解旋酶解开并促进端粒D环模型底物全长侵入链的释放。此外，在DNA-PKcs敲低的细胞中端粒G尾长度减少，而这种表型通过过表达WRN解旋酶得以逆转。这些结果表明，WRN和DNA-PKcs可能在体内协同防止G尾缩短。
