The plant homeodomain fingers of fission yeast Msc1 exhibit E3 ubiquitin ligase activity
The plant homeodomain fingers of fission yeast Msc1 exhibit E3 ubiquitin ligase activity
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DOI：
10.1074/jbc.m700729200
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发表时间：
2007-06-22
影响因子：
4.8
通讯作者：
Walworth, Nancy C.
中科院分区：
文献类型：
--
作者：
Dul, Barbara E.;Walworth, Nancy C.
DNA损伤检查点通路控制细胞如何调节细胞周期进程以响应DNA损伤。通过筛选在检查点通路中有缺陷的裂变酵母chk1突变体的抑制子，发现了一种新的分裂糖酵母pombe蛋白Msc1。Msc1包含3个植物同源结构域（PHD）指基序，其特征由C4HC3共识定义，类似于无名指结构域。病毒蛋白和细胞蛋白激酶MEKK1（丝裂原活化蛋白激酶/细胞外信号调节激酶激酶1）中的PHD指结构域与泛素E3蛋白连接酶有关，影响蛋白质稳定性。PHD指与RING指的密切结构关系表明，其他含有PHD结构域的蛋白可能也具有这种活性。我们发现Msc1的三个PHD指都可以作为泛素E3连接酶，首次报道了来自核蛋白的PHD指具有E3泛素连接酶活性。需要Msc1的PHD指的功能来挽救chk1 Delta菌株的DNA损伤敏感性。Msc1与人类泛素结合酶Ubc2的S. pombe同源物Rhp6共沉淀。引人注目的是，msc1的缺失完全抑制了rhp6缺失菌株的缓慢生长表型、紫外线和羟基脲敏感性，并恢复了在rhp6 Delta突变体中观察到的组蛋白H3甲基化缺陷。我们推测Msc1的E3泛素连接酶活性的靶点可能是染色质相关蛋白。
The DNA damage checkpoint pathway governs how cells regulate cell cycle progression in response to DNA damage. A screen for suppressors of a fission yeast chk1 mutant defective in the checkpoint pathway identified a novel Schizosaccharomyces pombe protein, Msc1. Msc1 contains 3 plant homeodomain (PHD) finger motifs, characteristically defined by a C4HC3 consensus similar to RING finger domains. PHD finger domains in viral proteins and in the cellular protein kinase MEKK1 (mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 1) have been implicated as ubiquitin E3 protein ligases that affect protein stability. The close structural relationship of PHD fingers to RING fingers suggests that other PHD domain-containing proteins might share this activity. We show that each of the three PHD fingers of Msc1 can act as ubiquitin E3 ligases, reporting for the first time that PHD fingers from a nuclear protein exhibit E3 ubiquitin ligase activity. The function of the PHD fingers of Msc1 is needed to rescue the DNA damage sensitivity of a chk1 Delta strain. Msc1 co-precipitates Rhp6, the S. pombe homologue of the human ubiquitin-conjugating enzyme Ubc2. Strikingly, deletion of msc1 confers complete suppression of the slow growth phenotype, UV and hydroxyurea sensitivities of an rhp6 deletion strain and restores deficient histone H3 methylation observed in the rhp6 Delta mutant. We speculate that the target of the E3 ubiquitin ligase activity of Msc1 is likely to be a chromatin-associated protein.