Department of Molecular Biology and Plant Virology, Institute of Biology, University of Stuttgart, Pfaffenwaldring 57, Stuttgart, Germany.
Virology. 2013 Aug 1;442(2):173-9. doi: 10.1016/j.virol.2013.04.012. Epub 2013 May 13.
The plant-infecting mastreviruses (family Geminiviridae) express two distinct replication-initiator proteins, Rep and RepA. Although RepA is essential for systemic infectivity, little is known about its precise function. We therefore investigated its role in replication using 2D-gel electrophoresis to discriminate the replicative forms of Maize streak virus (MSV) mutants that either fail to express RepA (RepA(-)), or express RepA that is unable to bind the plant retinoblastoma related protein, pRBR. Whereas amounts of viral DNA were reduced in two pRBR-binding deficient RepA mutants, their repertoires of replicative forms changed only slightly. While a complete lack of RepA expression was also associated with reduced viral DNA titres, the only traces of replicative intermediates of RepA(-) viruses were those indicative of recombination-dependent replication. We conclude that in MSV, RepA, but not RepA-pRBR binding, is necessary for single-stranded DNA production and efficient rolling circle replication.
侵染植物的麦束病毒（家族 Geminiviridae）表达两种不同的复制起始蛋白，Rep 和 RepA。尽管 RepA 对系统性感染是必需的，但它的确切功能知之甚少。因此，我们使用 2D-凝胶电泳来研究其在复制中的作用，以区分不能表达 RepA（RepA(-)）的玉米条纹病毒（MSV）突变体或表达不能与植物视网膜母细胞瘤相关蛋白 pRBR 结合的 RepA 的复制形式。虽然两个 pRBR 结合缺陷的 RepA 突变体中的病毒 DNA 量减少，但它们的复制形式谱变化很小。虽然完全缺乏 RepA 的表达也与病毒 DNA 滴度降低有关，但 RepA(-)病毒的复制中间体仅显示依赖重组的复制。我们得出结论，在 MSV 中，RepA（而不是 RepA-pRBR 结合）是单链 DNA 产生和有效滚环复制所必需的。
