The role of mismatched nucleotides in activating the hMSH2-hMSH6 Molecular Switch
The role of mismatched nucleotides in activating the hMSH2-hMSH6 Molecular Switch
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DOI：
10.1074/jbc.275.6.3922
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发表时间：
2000-02-11
影响因子：
4.8
通讯作者：
Fishel, R
中科院分区：
文献类型：
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作者：
Gradia, S;Acharya, S;Fishel, R
我们之前已经表明，hMSH2-hMSH6 含有一种内在 ATP 酶，该酶由错配引起的 ADP-->ATP 交换激活，协调诱导形成能够沿着 DNA 主链进行不依赖于水解的扩散的滑动夹 (1, 2)。这些研究表明，错配修复可以通过 ATP 结合的 hMSH2-hMSH6 分子开关扩散到 DNA 修复机制所转导的信号事件来传播。分子开关模型（Fishel, R, (1998) Genes Dev, 12, 2096-2101）与水解驱动易位模型（Blackwell, L. J.、Martik, D.、Bjornson, K. P.、Bjornson, E. S. 和 Modrich, P. (1998) J. Biol, Chem. 273, 32055-32062），并在证明水解无关扩散之外做出其他可测试的预测（Gradia, S., Subramanian, D., Wilson, T., Acharya, S., Makhov, A., Griffith, J., and Fishel, R, (1999) Mel. Cell 3, 255-261）：（i）个体错配引发的 ADP-->ATP 交换应该是唯一的和限速的，并且 (ii) DNA 刺激的 ATP 酶活性的 k(cat.DNA) 应随着链长度的增加而减小。在这里，我们检查了几种含有错配核苷酸的 DNA 底物的 hMSH2-hMSH6 亲和力和 ATP 酶刺激活性，以及生理条件下确定的错配的链长度依赖性。我们发现结果与分子开关模型的预测最为一致。
We have previously shown that hMSH2-hMSH6 contains an intrinsic ATPase which is activated by mismatch-provoked ADP-->ATP exchange that coordinately induces the formation of a sliding clamp capable of hydrolysis-independent diffusion along the DNA backbone (1, 2), These studies suggested that mismatch repair could be propagated by a signaling event transduced via diffusion of ATP-bound hMSH2-hMSH6 molecular switches to the DNA repair machinery. The Molecular Switch model (Fishel, R, (1998) Genes Dev, 12, 2096-2101) is considerably different than the Hydrolysis-Driven Translocation model (Blackwell, L. J., Martik, D., Bjornson, K. P., Bjornson, E. S., and Modrich, P. (1998) J. Biol, Chem. 273, 32055-32062) and makes additional testable predictions beyond the demonstration of hydrolysis-independent diffusion (Gradia, S., Subramanian, D., Wilson, T., Acharya, S., Makhov, A., Griffith, J., and Fishel, R, (1999) Mel. Cell 3, 255-261): (i) individual mismatch-provoked ADP-->ATP exchange should be unique and rate-limiting, and (ii) the k(cat.DNA) for the DNA-stimulated ATPase activity should decrease with increasing chain length. Here we have examined hMSH2-hMSH6 affinity and ATPase stimulatory activity for several DNA substrates containing mispaired nucleotides as well as the chain length dependence of a defined mismatch under physiological conditions. We find that the results are most consistent with the predictions of the Molecular Switch model.