Tight intramolecular regulation of the human Upf1 helicase by its N- and C-terminal domains.
Tight intramolecular regulation of the human Upf1 helicase by its N- and C-terminal domains.
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DOI：
10.1093/nar/gks1320
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发表时间：
2013-02-01
影响因子：
14.9
通讯作者：
Le Hir H
中科院分区：
文献类型：
--
作者：
Fiorini F;Boudvillain M;Le Hir H
RNA解旋酶Upf 1是一种多功能真核生物酶，参与DNA复制、端粒代谢和多种mRNA降解途径。Upf 1在无义介导的mRNA衰变（NMD）中发挥着核心作用，这是一个监视过程，它将过早翻译终止与mRNA降解及其保守伙伴Upf 2和Upf 3联系起来。在人类中，ATP依赖的RNA解旋酶活性和Upf 1的磷酸化都是NMD所必需的。当Upf 2结合其N-末端结构域时，Upf 1激活发生，将酶转换为活性形式。在这里，我们发现，Upf 1的C-末端结构域，在高等真核生物中保守，含有几个重要的磷酸化位点，也抑制侧翼解旋酶结构域。通过不同的生物化学方法，我们发现这个结构域，命名为SQ，直接与解旋酶结构域相互作用，以阻止ATP水解和RNA解旋。SQ结构域远端一半的磷酸化位点不直接参与这种抑制。因此，在缺乏多个结合伴侣的情况下，Upf 1通过两种分子内抑制机制安全地维持在非活性状态。这项研究强调了激活Upf 1等多功能RNA解旋酶所需的紧密而复杂的调控途径。
The RNA helicase Upf1 is a multifaceted eukaryotic enzyme involved in DNA replication, telomere metabolism and several mRNA degradation pathways. Upf1 plays a central role in nonsense-mediated mRNA decay (NMD), a surveillance process in which it links premature translation termination to mRNA degradation with its conserved partners Upf2 and Upf3. In human, both the ATP-dependent RNA helicase activity and the phosphorylation of Upf1 are essential for NMD. Upf1 activation occurs when Upf2 binds its N-terminal domain, switching the enzyme to the active form. Here, we uncovered that the C-terminal domain of Upf1, conserved in higher eukaryotes and containing several essential phosphorylation sites, also inhibits the flanking helicase domain. With different biochemical approaches we show that this domain, named SQ, directly interacts with the helicase domain to impede ATP hydrolysis and RNA unwinding. The phosphorylation sites in the distal half of the SQ domain are not directly involved in this inhibition. Therefore, in the absence of multiple binding partners, Upf1 is securely maintained in an inactive state by two intramolecular inhibition mechanisms. This study underlines the tight and intricate regulation pathways required to activate multifunctional RNA helicases like Upf1.
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