Integration host factor assembly at the cohesive end site of the bacteriophage lambda genome: implications for viral DNA packaging and bacterial gene regulation.
Integration host factor assembly at the cohesive end site of the bacteriophage lambda genome: implications for viral DNA packaging and bacterial gene regulation.
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在噬菌体lambda基因组的凝聚端位点的整合宿主因子组装：对病毒DNA包装和细菌基因调节的影响。
DOI：
10.1021/bi501025s
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发表时间：
2014-12-09
期刊：
影响因子：
2.9
通讯作者：
Catalano, Carlos Enrique
中科院分区：
文献类型：
--
作者：
Sanyal, Saurarshi J.;Yang, Teng-Chieh;Catalano, Carlos Enrique
整合宿主因子（IHF）是一种大肠杆菌蛋白，参与（i）细菌类核的缩合和（ii）多种细胞功能的调节。在其调节作用中，IHF与特定序列结合以将强弯曲引入DNA中;这提供了有助于位点特异性核蛋白复合物组装的双链体结构。或者，蛋白质可以以不依赖于序列的方式结合，该方式弱地弯曲和包裹双链体以促进类核形成。IHF也是几种病毒（包括λ噬菌体）发育所必需的，它促进裂解发育所需的基因组包装马达的位点特异性组装。多个IHF的共识序列已被确定在包装起始位点（COS），我们在这里询问IHF-COS结合相互作用，使用互补电泳迁移率变动（EMS）和分析超电泳（AUC）的方法。IHF识别cos（I1）内的单一共有序列，以提供强烈弯曲的核蛋白复合物。相比之下，IHF与非特异性DNA的结合较弱，但具有正协同性，以提供质量和凝聚水平不断增加的复合物系综。EMS和AUC数据的全局分析提供了IHF与I1和非特异性DNA底物结合的受限热力学结合常数和最近邻协同因子。在升高的IHF浓度下，核蛋白复合物经历了从凝聚到延伸的棒状构象的转变; IHF与I1的特异性结合赋予了该转变显著的能量屏障。这些结果提供了深入了解IHF如何在广泛的非特异性DNA缩合的背景下组装特异性调控复合物。
Integration host factor (IHF) is an Escherichia coli protein involved in (i) condensation of the bacterial nucleoid and (ii) regulation of a variety of cellular functions. In its regulatory role, IHF binds to a specific sequence to introduce a strong bend into the DNA; this provides a duplex architecture conducive to the assembly of site-specific nucleoprotein complexes. Alternatively, the protein can bind in a sequence-independent manner that weakly bends and wraps the duplex to promote nucleoid formation. IHF is also required for the development of several viruses, including bacteriophage lambda, where it promotes site-specific assembly of a genome packaging motor required for lytic development. Multiple IHF consensus sequences have been identified within the packaging initiation site (cos), and we here interrogate IHF–cos binding interactions using complementary electrophoretic mobility shift (EMS) and analytical ultracentrifugation (AUC) approaches. IHF recognizes a single consensus sequence within cos (I1) to afford a strongly bent nucleoprotein complex. In contrast, IHF binds weakly but with positive cooperativity to nonspecific DNA to afford an ensemble of complexes with increasing masses and levels of condensation. Global analysis of the EMS and AUC data provides constrained thermodynamic binding constants and nearest neighbor cooperativity factors for binding of IHF to I1 and to nonspecific DNA substrates. At elevated IHF concentrations, the nucleoprotein complexes undergo a transition from a condensed to an extended rodlike conformation; specific binding of IHF to I1 imparts a significant energy barrier to the transition. The results provide insight into how IHF can assemble specific regulatory complexes in the background of extensive nonspecific DNA condensation.
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