Modulation of the herpes simplex virus type-1 UL9 DNA helicase by its cognate single-strand DNA-binding protein, ICP8
Modulation of the herpes simplex virus type-1 UL9 DNA helicase by its cognate single-strand DNA-binding protein, ICP8
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DOI：
10.1074/jbc.m007219200
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发表时间：
2001-03-02
影响因子：
4.8
通讯作者：
Boehmer, PE
中科院分区：
文献类型：
--
作者：
Arana, ME;Haq, B;Boehmer, PE
使用单纯疱疹病毒1型UL 9 DNA解旋酶和ICP 8研究了其同源单链DNA结合蛋白刺激DNA解旋酶的机制。UL 9和ICP 8是病毒复制体的两个基本组分，它们结合成复合物以解开复制起点。UL 9的解旋酶和DNA刺激的ATP酶活性由于这种关联而大大升高。考虑到ICPS作为单链DNA结合蛋白，可以解释其刺激作用的最简单模型预测它将UL 9束缚在DNA模板上，从而增加其持续合成能力。与预测相反，本文提供的数据表明，ICP 8的刺激活性不依赖于其单链DNA结合活性。我们的数据支持另一种假设，即ICPS调节UL 9的活性。因此，数据显示UL 9的ICP 8结合位点构成了将解旋酶维持在低效基态的抑制区域。ICP 8通过中和该区域而充当正调节剂。ICP 8不影响底物结合、ATP水解或易位/DNA解旋的效率。相反，我们认为ICP 8增加了底物结合和ATP水解与易位/DNA解旋耦合的效率。
The mechanism of stimulation of a DNA helicase by its cognate single-strand DNA binding protein was examined using herpes simplex virus type-1 UL9 DNA helicase and ICP8. UL9 and ICP8 are two essential components of the viral replisome that associate into a complex to unwind the origins of replication. The helicase and DNA stimulated ATPase activities of UL9 are greatly elevated as a consequence of this association. Given that ICPS acts as a single strand DNA;binding protein, the simplest model that can account for its stimulatory effect predicts that it tethers UL9 to the DNA template, thereby increasing its processivity. In contrast to the prediction, data presented here show that the stimulatory activity of ICP8 does not depend on its single-strand DNA binding activity. Our data support an alternative hypothesis in which ICPS modulates the activity of UL9. Accordingly, the data show that the ICP8 binding site of UL9 constitutes an inhibitory region that maintains the helicase in an inefficient ground state. ICP8 acts as a positive regulator by neutralizing this region. ICP8 does not affect substrate binding, ATP hydrolysis, or the efficiency of translocation/DNA unwinding. Rather, we propose that ICP8 increases the efficiency with which substrate binding and ATP hydrolysis are coupled to translocation/DNA unwinding.