Insight into the Dual Functions of Bacterial Enhancer-Binding Protein Rrp2 of Borrelia burgdorferi
Insight into the Dual Functions of Bacterial Enhancer-Binding Protein Rrp2 of Borrelia burgdorferi
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DOI：
10.1128/jb.01010-15
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发表时间：
2016-03
影响因子：
3.2
通讯作者：
Yanping Yin;Youyun Yang;Xuwu Xiang;Qian Wang;Zhang-nv Yang;J. Blevins;Y. Lou;X. F. Yang
中科院分区：
文献类型：
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作者：
Yanping Yin;Youyun Yang;Xuwu Xiang;Qian Wang;Zhang-nv Yang;J. Blevins;Y. Lou;X. F. Yang
摘要RpoN-RpoS σ因子（σ54-σS）级联反应在莱姆病病原体伯氏疏螺旋体（Borrelia burgdorferi）的流行周期中的基因表达差异中起着重要作用。RpoN-RpoS通路由反应调节因子/σ54依赖性激活因子（也称为细菌增强子结合蛋白[bEBP]）Rrp 2激活。Rrp 2的一个独特特征是这种激活剂对于细胞复制是必需的，而RpoN-RpoS对于细菌生长是必需的。Rrp 2如何控制细胞复制，这是一个独立于RpoN-RpoS的功能，仍有待阐明。在这项研究中，通过产生一系列的条件rrp 2突变株，我们证明了N-末端受体结构域的Rrp 2所需的螺旋体的生长。此外，在Rrp 2的N末端内的磷酸化位点处的D52 A点突变废除了细胞复制。Rrp 2中心结构域内ATP酶基序的突变不影响螺旋体的复制，表明Rrp 2的磷酸化依赖性ATP酶活性对σ54活化不是细胞生长所必需的。然而，删除的C-末端结构域或16个氨基酸的螺旋-转角-螺旋（HTH）DNA结合基序内的C-末端结构域的Rrp 2废除螺旋体复制。结果表明，组成型表达的rpoS是有害的疏螺旋体的生长。我们表明，Rrp 2的本质不是由于对rpoS的影响。这些数据表明，Rrp 2的磷酸化依赖性寡聚化和DNA结合可能作为一种阻遏物，独立于σ54的激活，控制B中细胞复制的一个重要步骤。burgdorferi。细菌增强子结合蛋白（bEBP）是一组独特的转录激活因子，对σ54依赖的基因转录具有特异性。这项工作表明，B。伯氏螺旋体bEBP（Rrp 2）具有与σ54无关的额外功能，即其对于螺旋体生长的必要性，并且这种功能依赖于其N-末端信号结构域和C-末端DNA结合结构域。这些发现扩展了我们对bEBP的认识，并为进一步研究bEBP这种新功能的潜在机制提供了基础。
ABSTRACT It is well established that the RpoN-RpoS sigma factor (σ54-σS) cascade plays an essential role in differential gene expression during the enzootic cycle of Borrelia burgdorferi, the causative agent of Lyme disease. The RpoN-RpoS pathway is activated by the response regulator/σ54-dependent activator (also called bacterial enhancer-binding protein [bEBP]) Rrp2. One unique feature of Rrp2 is that this activator is essential for cell replication, whereas RpoN-RpoS is dispensable for bacterial growth. How Rrp2 controls cell replication, a function that is independent of RpoN-RpoS, remains to be elucidated. In this study, by generating a series of conditional rrp2 mutant strains, we demonstrated that the N-terminal receiver domain of Rrp2 is required for spirochetal growth. Furthermore, a D52A point mutation at the phosphorylation site within the N terminus of Rrp2 abolished cell replication. Mutation of the ATPase motif within the central domain of Rrp2 did not affect spirochetal replication, indicating that phosphorylation-dependent ATPase activity of Rrp2 for σ54 activation is not required for cell growth. However, deletion of the C-terminal domain or a 16-amino-acid truncation of the helix-turn-helix (HTH) DNA-binding motif within the C-terminal domain of Rrp2 abolished spirochetal replication. It was shown that constitutive expression of rpoS is deleterious to borrelial growth. We showed that the essential nature of Rrp2 is not due to an effect on rpoS. These data suggest that phosphorylation-dependent oligomerization and DNA binding of Rrp2 likely function as a repressor, independently of the activation of σ54, controlling an essential step of cell replication in B. burgdorferi. IMPORTANCE Bacterial enhancer-binding proteins (bEBPs) are a unique group of transcriptional activators specifically required for σ54-dependent gene transcription. This work demonstrates that the B. burgdorferi bEBP, Rrp2, has an additional function that is independent of σ54, that of its essentiality for spirochetal growth, and such a function is dependent on its N-terminal signal domain and C-terminal DNA-binding domain. These findings expand our knowledge on bEBP and provide a foundation to further study the underlying mechanism of this new function of bEBP.