Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, Taiwan.
PLoS One. 2013 Jul 25;8(7):e70037. doi: 10.1371/journal.pone.0070037. Print 2013.
Geminiviruses are known to exhibit both prokaryotic and eukaryotic features in their genomes, with the ability to express their genes and even replicate in bacterial cells. We have demonstrated previously the existence of unit-length single-stranded circular DNAs of Ageratum yellow vein virus (AYVV, a species in the genus Begomovirus, family Geminiviridae) in Escherichia coli cells, which prompted our search for unknown prokaryotic functions in the begomovirus genomes. By using a promoter trapping strategy, we identified a novel prokaryotic promoter, designated AV3 promoter, in nts 762-831 of the AYVV genome. Activity assays revealed that the AV3 promoter is strong, unidirectional, and constitutive, with an endogenous downstream ribosome binding site and a translatable short open reading frame of eight amino acids. Sequence analyses suggested that the AV3 promoter might be a remnant of prokaryotic ancestors that could be related to certain promoters of bacteria from marine or freshwater environments. The discovery of the prokaryotic AV3 promoter provided further evidence for the prokaryotic origin in the evolutionary history of geminiviruses.
双生病毒在其基因组中表现出原核和真核生物的特征，能够表达其基因，甚至在细菌细胞中复制。我们之前已经证明，在大肠杆菌细胞中存在矮牵牛黄脉病毒（AYVV，属于双生病毒科的菜豆金色花叶病毒属）的全长单链环状 DNA，这促使我们在双生病毒基因组中寻找未知的原核功能。通过使用启动子捕获策略，我们在 AYVV 基因组的 nts762-831 中鉴定出一个新的原核启动子，命名为 AV3 启动子。活性测定显示，AV3 启动子是强的、单向的和组成型的，具有内源性下游核糖体结合位点和可翻译的 8 个氨基酸的短开放阅读框。序列分析表明，AV3 启动子可能是原核祖先的残余物，与海洋或淡水环境中的某些细菌启动子有关。原核 AV3 启动子的发现为双生病毒进化史上的原核起源提供了进一步的证据。
