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腾讯登录Mol Microbiol：揭示Hda蛋白维持大肠杆菌细胞生存的新证据
| 导读 | 近日，国际著名杂志<em>Molecular Microbiology</em>上刊登了纽约州立大学研究者的最新研究成果“Evidence for roles of the Escherichia coli Hda protein beyond regulatory inactivation of DnaA”，文章中，研究者揭示了大肠杆菌Hda蛋白在维持细胞生存上的重要功能... |
近日，国际著名杂志<em>Molecular Microbiology</em>上刊登了纽约州立大学研究者的最新研究成果“Evidence for roles of the Escherichia coli Hda protein beyond regulatory inactivation of DnaA”，文章中，研究者揭示了大肠杆菌Hda蛋白在维持细胞生存上的重要功能及证据。
大肠杆菌，又名肠埃希氏菌(E. coli)，某些大肠杆菌菌群对人和动物有致病性，尤其对婴儿和幼畜，常引起严重腹泻和败血症。大肠杆菌中ATP紧密形式的DnaA蛋白可以在复制起点Oric位置或者某些基因的操纵子部位结合其DnaA盒子（DnaA Boxes），最终开始其复制转录起始。
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Hda蛋白和其β滑行夹子一起可以通过钝化DnaA（DnaA的调解失活，RIDA）来激活其ATP酶活性，最终在DNA复制水平来调节DnaA的活性。
在文章中，研究者使用了大肠杆菌<em>dnaN159</em>的突变体，其可以表达β159“夹子蛋白质”来获得Hada蛋白协调复制的活性行为。Had的高表达可以在两种水平（Pol II和Pol IV）来阻碍大肠杆菌dnaN159的突变体的生长，这就表明Hda可以作为管理者来管理Pols的活动的角色。Hda的高水平表达也和食品添加剂-硝基糠棕的敏感性直接相关。
使用大肠杆菌<em>dnaN159</em>的突变体，研究者发现了24个新的hda的等位基因，其中有四个可以在RIDA缺失的情况下支持大肠杆菌的活力。因此研究者的研究揭示了Hda对于细胞生存维持的功能角色，DnaA的调节失活也许并不是必须的。
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<img src="http://www.bioon.com/biology/UploadFiles/201208/2012080823033336.jpg" alt="" width="113" height="149" border="0" />
<a title="" href="http://dx.doi.org/doi:10.1111/j.1365-2958.2012.08129.x" target="_blank">doi:10.1111/j.1365-2958.2012.08129.x</a>
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PMID:
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<br/><strong>Evidence for roles of the Escherichia coli Hda protein beyond regulatory inactivation of DnaA</strong><br/>
Jamie C. Baxter1,2, Mark D. Sutton1,2,*
The ATP-bound form of the Escherichia coli DnaA protein binds ‘DnaA boxes’ present in the origin of replication (oriC) and operator sites of several genes, including dnaA, to co-ordinate their transcription with initiation of replication. The Hda protein, together with the β sliding clamp, stimulates the ATPase activity of DnaA via a process termed regulatory inactivation of DnaA (RIDA), to regulate the activity of DnaA in DNA replication. Here, we used the mutant dnaN159 strain, which expresses the β159 clamp protein, to gain insight into how the actions of Hda are co-ordinated with replication. Elevated expression of Hda impeded growth of the dnaN159 strain in a Pol II- and Pol IV-dependent manner, suggesting a role for Hda managing the actions of these Pols. In a wild-type strain, elevated levels of Hda conferred sensitivity to nitrofurazone, and suppressed the frequency of −1 frameshift mutations characteristic of Pol IV, while loss of hda conferred cold sensitivity. Using the dnaN159 strain, we identified 24 novel hda alleles, four of which supported E. coli viability despite their RIDA defect. Taken together, these findings suggest that although one or more Hda functions are essential for cell viability, RIDA may be dispensable.
<br/>来源：生物谷
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大肠杆菌，又名肠埃希氏菌(E. coli)，某些大肠杆菌菌群对人和动物有致病性，尤其对婴儿和幼畜，常引起严重腹泻和败血症。大肠杆菌中ATP紧密形式的DnaA蛋白可以在复制起点Oric位置或者某些基因的操纵子部位结合其DnaA盒子（DnaA Boxes），最终开始其复制转录起始。
<!--more-->
Hda蛋白和其β滑行夹子一起可以通过钝化DnaA（DnaA的调解失活，RIDA）来激活其ATP酶活性，最终在DNA复制水平来调节DnaA的活性。
在文章中，研究者使用了大肠杆菌<em>dnaN159</em>的突变体，其可以表达β159“夹子蛋白质”来获得Hada蛋白协调复制的活性行为。Had的高表达可以在两种水平（Pol II和Pol IV）来阻碍大肠杆菌dnaN159的突变体的生长，这就表明Hda可以作为管理者来管理Pols的活动的角色。Hda的高水平表达也和食品添加剂-硝基糠棕的敏感性直接相关。
使用大肠杆菌<em>dnaN159</em>的突变体，研究者发现了24个新的hda的等位基因，其中有四个可以在RIDA缺失的情况下支持大肠杆菌的活力。因此研究者的研究揭示了Hda对于细胞生存维持的功能角色，DnaA的调节失活也许并不是必须的。
<div id="ztload">
<div>
<div>
<img src="http://www.bioon.com/biology/UploadFiles/201208/2012080823033336.jpg" alt="" width="113" height="149" border="0" />
<a title="" href="http://dx.doi.org/doi:10.1111/j.1365-2958.2012.08129.x" target="_blank">doi:10.1111/j.1365-2958.2012.08129.x</a>
PMC:
PMID:
</div>
<div>
<br/><strong>Evidence for roles of the Escherichia coli Hda protein beyond regulatory inactivation of DnaA</strong><br/>
Jamie C. Baxter1,2, Mark D. Sutton1,2,*
The ATP-bound form of the Escherichia coli DnaA protein binds ‘DnaA boxes’ present in the origin of replication (oriC) and operator sites of several genes, including dnaA, to co-ordinate their transcription with initiation of replication. The Hda protein, together with the β sliding clamp, stimulates the ATPase activity of DnaA via a process termed regulatory inactivation of DnaA (RIDA), to regulate the activity of DnaA in DNA replication. Here, we used the mutant dnaN159 strain, which expresses the β159 clamp protein, to gain insight into how the actions of Hda are co-ordinated with replication. Elevated expression of Hda impeded growth of the dnaN159 strain in a Pol II- and Pol IV-dependent manner, suggesting a role for Hda managing the actions of these Pols. In a wild-type strain, elevated levels of Hda conferred sensitivity to nitrofurazone, and suppressed the frequency of −1 frameshift mutations characteristic of Pol IV, while loss of hda conferred cold sensitivity. Using the dnaN159 strain, we identified 24 novel hda alleles, four of which supported E. coli viability despite their RIDA defect. Taken together, these findings suggest that although one or more Hda functions are essential for cell viability, RIDA may be dispensable.
<br/>来源：生物谷
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