Burns T M, Harding R M, Dale J L
Centre for Molecular Biotechnology, School of Life Science, Queensland University of Technology, Brisbane, Australia.
J Gen Virol. 1995 Jun;76 ( Pt 6):1471-82. doi: 10.1099/0022-1317-76-6-1471.
We have cloned, sequenced and analysed an additional five circular ssDNA components of banana bunchy top virus (BBTV) which we have called components 2, 3, 4, 5 and 6. These components were present in all BBTV infections tested. Four of these components (components 3, 4, 5 and 6) had one large open reading frame (ORF) in the virion sense located 3' of a stem-loop structure. Each ORF had a potential TATA box and one or two potential polyadenylation signals associated with it and each polyadenylation signal had an associated GC-rich region containing the trinucleotide sequence TTG. A number of ORFs were identified in component 2 but none of these had appropriately located potential TATA boxes and polyadenylation signals associated with them. None of the ORF amino acid sequences nor the full DNA sequences of any of the components had significant sequence identity with any known protein or nucleic acid sequences. However, the ORF of component 4 encoded a 30 residue hydrophobic domain which may indicate that this ORF encoded a transmembrane protein. Further, the ORFs of components 3 and 5 potentially encoded proteins of about 20 kDa, the size of the BBTV coat protein. There were two regions of sequence identity between the five components described here and the previously described component 1. Each component contained a conserved stem-loop structure and a nonanucleotide potential TATA box which was 5' of the large virion-sense ORF in five of the components. The stem-loop structures were incorporated in a common region (CR-SL) of 69 nucleotides which was 62% identical between components. All six BBTV components also contained a major common region (CR-M) which was located 5' of the CR-SL in each component, in the non-coding region and was 76% identical over 92 nucleotides. Each CR-M contained a near-complete 16 nucleotide direct repeat and a GC-box which was similar to the rightward promoter element found in wheat dwarf geminivirus. From these results, BBTV appears to belong to an undescribed plant virus group which could also include subterranean clover stunt virus, coconut foliar decay virus, faba bean necrotic yellows virus and milk vetch dwarf virus.
我们克隆、测序并分析了香蕉束顶病毒（BBTV）另外五个环状单链DNA组分，分别命名为组分2、3、4、5和6。在所检测的所有BBTV感染样本中均存在这些组分。其中四个组分（组分3、4、5和6）在病毒链方向上有一个大的开放阅读框（ORF），位于茎环结构的3'端。每个ORF都有一个潜在的TATA框以及一个或两个与之相关的潜在多聚腺苷酸化信号，每个多聚腺苷酸化信号都有一个与之相关的富含GC的区域，包含三核苷酸序列TTG。在组分2中鉴定出了多个ORF，但这些ORF均没有与之相关的位置合适的潜在TATA框和多聚腺苷酸化信号。这些组分的ORF氨基酸序列或完整DNA序列与任何已知蛋白质或核酸序列均无显著序列同一性。然而，组分4的ORF编码了一个30个残基的疏水域，这可能表明该ORF编码一种跨膜蛋白。此外，组分3和5的ORF可能编码约20 kDa的蛋白质，与BBTV外壳蛋白的大小相同。此处描述的五个组分与先前描述的组分1之间存在两个序列同一性区域。每个组分都包含一个保守的茎环结构和一个九核苷酸潜在TATA框，在五个组分中，该框位于病毒链方向大ORF的5'端。茎环结构包含在一个69个核苷酸的共同区域（CR-SL）中，各组分之间该区域的同一性为62%。所有六个BBTV组分还包含一个主要共同区域（CR-M），该区域位于每个组分CR-SL的5'端，在非编码区，92个核苷酸上的同一性为76%。每个CR-M都包含一个近乎完整的16个核苷酸的直接重复序列和一个GC框，与小麦矮缩双生病毒中发现的向右启动子元件相似。根据这些结果，BBTV似乎属于一个未描述的植物病毒组，该组可能还包括地下三叶草矮化病毒、椰子叶腐烂病毒、蚕豆坏死黄化病毒和紫云英矮化病毒。
