Todd D, Creelan J L, Meehan B M, McNulty M S
Department of Agriculture for Northern Ireland.
Arch Virol. 1996;141(8):1523-34. doi: 10.1007/BF01718252.
Chicken anaemia virus (CAV) is an icosahedral virus, 25 nm in diameter, which, on the basis of its circular single-stranded DNA genome, has recently been classified in the family, Circoviridae. We have investigated whether infectious, monomeric CAV DNA from recombinant plasmids containing tandemly-repeated CAV replicative form (RF) DNAs, following transfection, was generated by homologous recombination or a replicational release mechanism involving rolling circle replication (RCR) of DNA. Experiments designed to locate the virus strand origin of RCR and/or sites of recombination were performed by sequence analyses of hybrid viruses generated after transfection with cloned tandemly-repeated RFs specified by the sequence-distinct Cux-1 and 26P4 isolates. Positive transfection results obtained from 2 recombinant plasmid constructs were shown to have resulted from homologous recombination occurring at different sites within the RF sequence. Three of 5 hybrid viruses analysed were "circularised" within the same 105 bp sequence, that contains four 19bp repeats and with which promoter/enhancer activity has been associated. This region may represent a novel origin or recombination hot-spot within the CAV genome. A distinctive cruciform-loop structure within the non-coding region was shown to contain an S1 nuclease-sensitive site, detected in CAV RF and in recombinant plasmids containing RF inserts.
鸡贫血病毒（CAV）是一种直径为25纳米的二十面体病毒，基于其环状单链DNA基因组，最近被归类于圆环病毒科。我们研究了转染后，含有串联重复CAV复制形式（RF）DNA的重组质粒中具有感染性的单体CAV DNA是通过同源重组产生的，还是通过涉及DNA滚环复制（RCR）的复制释放机制产生的。通过对由序列不同的Cux-1和26P4分离株指定的克隆串联重复RF转染后产生的杂交病毒进行序列分析，开展了旨在定位RCR的病毒链起源和/或重组位点的实验。从2种重组质粒构建体获得的阳性转染结果表明，其是由RF序列内不同位点发生的同源重组导致的。分析的5种杂交病毒中有3种在相同的105碱基对序列内“环化”，该序列包含四个19碱基对的重复序列，且与启动子/增强子活性相关。该区域可能代表CAV基因组内一个新的起源或重组热点。非编码区内一种独特的十字形环结构显示含有一个S1核酸酶敏感位点，在CAV RF和含有RF插入片段的重组质粒中均可检测到。
