Forster A C, Davies C, Sheldon C C, Jeffries A C, Symons R H
Department of Biochemistry, University of Adelaide, South Australia.
Nature. 1988 Jul 21;334(6179):265-7. doi: 10.1038/334265a0.
Avocado sunblotch viroid (ASBV) is a 247-nucleotide, single-stranded, circular RNA. It is considered to replicate via a rolling-circle mechanism in which circular, monomeric plus and minus RNAs act as templates for the synthesis of longer-than-unit-length precursor RNAs. Processing of these RNAs in vivo may occur by a self-cleavage reaction, as indicated by ability of dimeric, linear plus and minus ASBV RNAs to specifically self-cleave in vitro with the excision of a monomeric RNA with 5'-hydroxyl and 2',3'-cyclic phosphodiester termini. A similar self-cleavage reaction has also been reported to occur in an RNA transcript containing a dimeric copy of a tandemly repeated, 330-base-pair sequence of the newt genome. Based on comparisons with self-cleaving plant viral satellite RNAs, hammerhead-shaped active structures, each containing one self-cleavage site, were proposed for the plus and minus ASBV RNAs and the newt RNA, but the stability of these hammerheads has been questioned. Here, more stable active structures that contain two self-cleavage sites are proposed and data supporting these models are presented.
鳄梨日斑类病毒（ASBV）是一种由247个核苷酸组成的单链环状RNA。它被认为通过滚环机制进行复制，在该机制中，环状的单体正链和负链RNA作为模板用于合成比单位长度更长的前体RNA。体内这些RNA的加工可能通过自我切割反应发生，二聚体、线性正链和负链ASBV RNA在体外能够特异性自我切割并切除具有5'-羟基和2',3'-环磷酸二酯末端的单体RNA，这表明了这一点。据报道，在含有蝾螈基因组串联重复的330个碱基对序列的二聚体拷贝的RNA转录物中也发生了类似的自我切割反应。基于与自我切割的植物病毒卫星RNA的比较，有人提出正链和负链ASBV RNA以及蝾螈RNA具有锤头状活性结构，每个结构包含一个自我切割位点，但这些锤头结构的稳定性受到了质疑。在此，我们提出了包含两个自我切割位点的更稳定的活性结构，并展示了支持这些模型的数据。
