Carstens Eric B, Wu Yuntao
Department of Microbiology and Immunology, Queen's University, Kingston, ON K7L 3N6, Canada.
J Gen Virol. 2007 Jan;88(Pt 1):114-122. doi: 10.1099/vir.0.82384-0.
The presence of homologous repeat (hr) regions in multiple locations within baculovirus genomes has led to the hypothesis that they represent origins of DNA replication. This hypothesis has been supported by transient replication assays where plasmids carrying hrs replicated in the presence of virus DNA replication. This study investigated whether any specific hr region was essential for viral DNA replication in vivo, by generating a series of recombinant Autographa californica multiple nucleopolyhedrovirus where the lacZ gene replaced hr1, hr1a, hr2, hr3, hr4a or hr4b. In addition, a double-hr knockout virus was constructed where both hr2 and hr3 were deleted. The successful construction of these knockout viruses indicated that no specific region was essential for virus production. These recombinant viruses were characterized by titrations of budded virus, expression of a variety of virus-specific proteins and the synthesis of viral DNA at various times after infection. The results demonstrated that each hr was dispensable for all of these properties and that no single region was absolutely essential for virus replication in cell culture. The functional significance of multiple origin regions is still unclear.
杆状病毒基因组内多个位置存在同源重复（hr）区域，这引发了一种假说，即它们代表DNA复制起点。这一假说得到了瞬时复制试验的支持，在该试验中，携带hrs的质粒在病毒DNA复制存在的情况下进行复制。本研究通过构建一系列重组苜蓿银纹夜蛾多核型多角体病毒来研究是否有任何特定的hr区域对体内病毒DNA复制至关重要，在这些重组病毒中，lacZ基因取代了hr1、hr1a、hr2、hr3、hr4a或hr4b。此外，构建了一种双hr敲除病毒，其中hr2和hr3均被删除。这些敲除病毒的成功构建表明，没有特定区域对病毒产生是必不可少的。通过对出芽病毒进行滴定、检测多种病毒特异性蛋白的表达以及在感染后不同时间检测病毒DNA的合成，对这些重组病毒进行了表征。结果表明，每个hr对于所有这些特性都是可有可无的，并且没有单个区域对于细胞培养中的病毒复制是绝对必不可少的。多个起源区域的功能意义仍不清楚。
