Molecular and Computational Biology Program, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA.
Cell Rep. 2013 Apr 25;3(4):1117-27. doi: 10.1016/j.celrep.2013.03.002. Epub 2013 Mar 28.
The DNA tumor virus Simian virus 40 (SV40) is a model system for studying eukaryotic replication. SV40 large tumor antigen (LTag) is the initiator/helicase that is essential for genome replication. LTag recognizes and assembles at the viral replication origin. We determined the structure of two multidomain LTag subunits bound to origin DNA. The structure reveals that the origin binding domains (OBDs) and Zn and AAA+ domains are involved in origin recognition and assembly. Notably, the OBDs recognize the origin in an unexpected manner. The histidine residues of the AAA+ domains insert into a narrow minor groove region with enhanced negative electrostatic potential. Computational analysis indicates that this region is intrinsically narrow, demonstrating the role of DNA shape readout in origin recognition. Our results provide important insights into the assembly of the LTag initiator/helicase at the replication origin and suggest that histidine contacts with the minor groove serve as a mechanism of DNA shape readout.
猿猴病毒 40（SV40）是一种研究真核复制的模式系统。SV40 大肿瘤抗原（LTag）是启动子/解旋酶，对于基因组复制是必不可少的。LTag 识别并组装在病毒复制起点处。我们确定了两个多结构域 LTag 亚基与起源 DNA 结合的结构。该结构表明，起源结合结构域（OBD）和 Zn 和 AAA+结构域参与了起源识别和组装。值得注意的是，OBD 以一种意想不到的方式识别起源。AAA+结构域的组氨酸残基插入到具有增强负静电势的狭窄小沟区域。计算分析表明，该区域本质上较窄，证明了 DNA 形状读取在起源识别中的作用。我们的研究结果提供了有关 LTag 启动子/解旋酶在复制起点处组装的重要见解，并表明组氨酸与小沟的接触是 DNA 形状读取的一种机制。
