Schnölzer M, Haas B, Raam K, Hofmann H, Sänger H L
Abteilung Viroidforschung and Rechenzentrum, Max-Planck-Institut für Biochemie, D-8033, Martinsried, FRG.
EMBO J. 1985 Sep;4(9):2181-90. doi: 10.1002/j.1460-2075.1985.tb03913.x.
Sequence analysis by primer-extension at the level of their cDNA showed that the RNA genomes of various field isolates of potato spindle tuber viroid (PSTV) of different virulence differ from each other only in a few nucleotides in two distinct regions of the rod-shaped molecule. Despite insertions and deletions the chain length of 359 nucleotides is strictly conserved in all the isolates studied. Thermodynamic calculations revealed that due to the observed sequence differences the region located at the left hand part of the rod-like secondary structure of the PSTV molecule, denoted 'virulence modulating (VM) region', becomes increasingly unstable with the increasing virulence of the corresponding isolate. Based on these data we propose in molecular terms a model for the mechanism of viroid pathogenicity. It implies that the nucleotides of the VM region specify and modulate the binding- and hence the competition-potential of the PSTV RNA molecule for a still unknown host factor(s) and thus determine the virulence of PSTV.
通过对其cDNA水平进行引物延伸的序列分析表明,不同毒力的马铃薯纺锤块茎类病毒(PSTV)各种田间分离株的RNA基因组,在棒状分子的两个不同区域仅在少数核苷酸上彼此不同。尽管存在插入和缺失,但在所有研究的分离株中,359个核苷酸的链长严格保守。热力学计算表明,由于观察到的序列差异,位于PSTV分子棒状二级结构左手部分的区域,称为“毒力调节(VM)区域”,随着相应分离株毒力的增加而变得越来越不稳定。基于这些数据,我们从分子角度提出了一个类病毒致病机制的模型。这意味着VM区域的核苷酸指定并调节PSTV RNA分子与一个仍未知的宿主因子的结合,进而调节其竞争潜力,从而决定PSTV的毒力。