Hipp Katharina, Rau Peter, Schäfer Benjamin, Pfannstiel Jens, Jeske Holger
University of Stuttgart, Institute of Biomaterials and biomolecular Systems, Department of Molecular Biology and Plant Virology, Pfaffenwaldring 57, 70550 Stuttgart, Germany.
University of Stuttgart, Institute of Biomaterials and biomolecular Systems, Department of Molecular Biology and Plant Virology, Pfaffenwaldring 57, 70550 Stuttgart, Germany.
Virology. 2016 Nov;498:136-148. doi: 10.1016/j.virol.2016.07.011. Epub 2016 Aug 30.
Plant infecting geminiviruses encode a small (A)C4 protein within the open reading frame of the replication-initiator protein. In African cassava mosaic virus, two in-frame start codons may be used for the translation of a longer and a shorter AC4 variant. Both were fused to green fluorescent protein or glutathione-S-transferase genes and expressed in fission yeast. The longer variant accumulated in discrete spots in the cytoplasm, whereas the shorter variant localized to the plasma membrane. A similar expression pattern was found in plants. A myristoylation motif may promote a targeting of the shorter variant to the plasma membrane. Mass spectrometry analysis of the yeast-expressed shorter variant detected the corresponding myristoylation. The biological relevance of the second start codon was confirmed using mutated infectious clones. Whereas mutating the first start codon had no effect on the infectivity in Nicotiana benthamiana plants, the second start codon proved to be essential.
侵染植物的双生病毒在复制起始蛋白的开放阅读框内编码一种小的（A）C4蛋白。在非洲木薯花叶病毒中，两个读码框内的起始密码子可用于翻译较长和较短的AC4变体。二者均与绿色荧光蛋白或谷胱甘肽-S-转移酶基因融合，并在裂殖酵母中表达。较长的变体在细胞质中的离散斑点中积累，而较短的变体定位于质膜。在植物中也发现了类似的表达模式。豆蔻酰化基序可能促进较短变体靶向质膜。对酵母表达的较短变体进行质谱分析检测到了相应的豆蔻酰化。使用突变的感染性克隆证实了第二个起始密码子的生物学相关性。虽然突变第一个起始密码子对本氏烟草植株的感染性没有影响，但第二个起始密码子被证明是必不可少的。
