Chrysanthemum chlorotic mottle viroid: Unusual structural properties of a subgroup of self-cleaving viroids with hammerhead ribozymes
Chrysanthemum chlorotic mottle viroid: Unusual structural properties of a subgroup of self-cleaving viroids with hammerhead ribozymes
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DOI：
10.1073/pnas.94.21.11262
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发表时间：
1997-10-14
影响因子：
11.1
通讯作者：
Flores, R
中科院分区：
文献类型：
--
作者：
Navarro, B;Flores, R
菊花褪绿斑驳病（CChh 4）的病原已被鉴定、克隆和测序，它是一个398-399个核苷酸的类病毒RNA（CChMVd），具有完整CChMVd序列的离体转录本具有感染性，能引起CChM病的典型症状，CChMVd在两条极性链上都能形成锤头状结构，正和负单体CChMVd RNA在体外转录过程中和纯化后自切割，如这些结构所预测的，其是稳定的，并且最有可能作为单个锤头结构，如在桃潜伏花叶类病毒（PLMVd）中，而在鳄梨日斑类病毒（ASBVd）中则没有。此外，正CChMVd锤头状结构在体内似乎也有活性，因为从感染组织中分离的线性正CChMVd RNA的5'末端与相应锤头状核酶预测的相同。CChMVd的两种锤头结构都显示出一些特点：正自切割结构域在保守的A9残基之后具有未配对的A，负自切割结构域具有异常长的螺旋II。CChMVd预测的最稳定的二级结构是分支构象，其不满足为除PLMVd之外的大多数类病毒的体外结构提出的棒状或准棒状模型，其提出的最低自由能的二级结构也是分支的。CChMVd和PLMVd的不寻常构象由它们在2 M LiCl中的不溶性支持，与ASBVd和一系列在相同高盐条件下可溶的代表性非自裂解类病毒相反，这些结果支持将自裂解类病毒分为两个亚组，一个由ASBVd形成，另一个由PLMVd和CChMVd形成。
The causal agent of chrysanthemum chlorotic mottle (CChh4) disease has been identified, cloned, and sequenced, It is a viroid RNA (CChMVd) of 398-399 nucleotides, In vitro transcripts with the complete CChMVd sequence were infectious and induced the typical symptoms of the CChM disease, CChMVd can form hammerhead structures in both polarity strands, Plus and minus monomeric CChMVd RNAs self-cleaved during in vitro transcription and after purification as predicted by these structures, which are stable and most probably act as single hammerhead structures as in peach latent mosaic viroid (PLMVd), but not in avocado sunblotch viroid (ASBVd), Moreover, the plus CChMVd hammerhead structure also appears to be active in vivo, because the 5' terminus of the linear plus CChMVd RNA isolated from infected tissue is that predicted by the corresponding hammerhead ribozyme. Both hammerhead structures of CChMVd display some peculiarities: the plus self-cleaving domain has an unpaired A after the conserved A9 residue, and the minus one has an unusually long helix II, The most stable secondary structure predicted for CChMVd is a branched conformation that does not fulfill the rod-like or quasi-rod-like model proposed for the in vitro structure of most viroids with the exception of PLMVd, whose proposed secondary structure of lowest free energy also is branched, The unusual conformation of CChMVd and PLMVd is supported by their insolubility in 2 M LiCl, in contrast to ASBVd and a series of representative non-self-cleaving viroids that are soluble under the same high salt conditions, These results support the classification of self-cleaving viroids into two subgroups, one formed by ASBVd and the other one by PLMVd and CChMVd.