Rif2 与 Rad50 的相互作用通过释放 Tel1 与 MRX 的结合来拮抗 Tel1 在检查点信号传导和 DNA 连接中的功能。

Rif2 interaction with Rad50 counteracts Tel1 functions in checkpoint signalling and DNA tethering by releasing Tel1 from MRX binding.

机构信息

Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano - Bicocca, 20126 Milano, Italy.

出版信息

Nucleic Acids Res. 2024 Mar 21;52(5):2355-2371. doi: 10.1093/nar/gkad1246.

Abstract

The yeast Rif2 protein is known to inhibit Mre11 nuclease and the activation of Tel1 kinase through a short motif termed MIN, which binds the Rad50 subunit and simulates its ATPase activity in vitro. The mechanism by which Rif2 restrains Tel1 activation and the consequences of this inhibition at DNA double-strand breaks (DSBs) are poorly understood. In this study, we employed AlphaFold-Multimer modelling to pinpoint and validate the interaction surface between Rif2 MIN and Rad50. We also engineered the rif2-S6E mutation that enhances the inhibitory effect of Rif2 by increasing Rif2-Rad50 interaction. Unlike rif2Δ, the rif2-S6E mutation impairs hairpin cleavage. Furthermore, it diminishes Tel1 activation by inhibiting Tel1 binding to DSBs while leaving MRX association unchanged, indicating that Rif2 can directly inhibit Tel1 recruitment to DSBs. Additionally, Rif2S6E reduces Tel1-MRX interaction and increases stimulation of ATPase by Rad50, indicating that Rif2 binding to Rad50 induces an ADP-bound MRX conformation that is not suitable for Tel1 binding. The decreased Tel1 recruitment to DSBs in rif2-S6E cells impairs DSB end-tethering and this bridging defect is suppressed by expressing a Tel1 mutant variant that increases Tel1 persistence at DSBs, suggesting a direct role for Tel1 in the bridging of DSB ends.

摘要

酵母 Rif2 蛋白通过一个短基序 MIN 抑制 Mre11 核酸酶和 Tel1 激酶的激活,该基序结合 Rad50 亚基并在体外模拟其 ATP 酶活性。Rif2 抑制 Tel1 激活的机制以及这种抑制在 DNA 双链断裂(DSB)中的后果知之甚少。在这项研究中,我们采用了 AlphaFold-Multimer 建模来确定 Rif2 MIN 和 Rad50 之间的相互作用表面,并进行了验证。我们还构建了 rif2-S6E 突变体,通过增加 Rif2-Rad50 相互作用来增强 Rif2 的抑制作用。与 rif2Δ 不同,rif2-S6E 突变体损害发夹切割。此外,它通过抑制 Tel1 与 DSB 的结合来抑制 Tel1 的激活,而不改变 MRX 关联,表明 Rif2 可以直接抑制 Tel1 招募到 DSB。此外,Rif2S6E 减少了 Tel1-MRX 相互作用并增加了 Rad50 的 ATP 酶刺激,表明 Rif2 结合 Rad50 诱导不适合 Tel1 结合的 ADP 结合的 MRX 构象。 Rif2-S6E 细胞中 Tel1 招募到 DSB 的减少会损害 DSB 端连接,而表达增加 Tel1 在 DSB 上持久性的 Tel1 突变体可抑制这种桥接缺陷,表明 Tel1 在 DSB 端桥接中具有直接作用。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/1c86/10954470/3367eb863c31/gkad1246figgra1.jpg

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