Domdey H, Jank P, Sänger L, Gross H J
Nucleic Acids Res. 1978 Apr;5(4):1221-36. doi: 10.1093/nar/5.4.1221.
Potato spindle tuber viroid (PSTV), a small infectios RNA, has been completely digested with RNase T1 and RNase A, and the resulting oligonucleotides have been sequenced using 5'-terminal 32p-labelling with gamma-32p ATP and T4 polynucleotide kinase, fingerprinting and controlled nuclease P1 digestion. Modified nucleotides have not been detected in 5'-positions of these oligonucleotides. PSTV consists of about 359 nucleotides and contains a remarkable stretch of 18 purines, mainly adenosines; there is no AUG initiation triplet present. The established oligonucleotide sequences preclude a perfect intramolecular base complementarity within the covalently closed viroid circle. Therefore, the rigid, rod-like native secondary structure of PSTV, as seen in the electron microscope, must be based on a defective rather than on a homogeneous RNA helix. The detailed analysis of the bisulfite-catalized modification of cytidine to uridine in PSTV revealed a higher reactivity for the majority of the cytidines than would be expected for a perfect helix. Since only cytidines in single-stranded regions are knonw to be fully reactive, this finding provides additional evidence for defects in the helical secondary structure of PSTV.
马铃薯纺锤块茎类病毒（PSTV）是一种小的感染性RNA，已用核糖核酸酶T1和核糖核酸酶A完全消化，所得的寡核苷酸已通过使用γ-32P ATP和T4多核苷酸激酶进行5'-末端32P标记、指纹图谱分析和受控核酸酶P1消化进行测序。在这些寡核苷酸的5'-位置未检测到修饰核苷酸。PSTV由约359个核苷酸组成，包含一段由18个嘌呤（主要是腺苷）组成的显著序列；不存在AUG起始三联体。已确定的寡核苷酸序列排除了共价闭合类病毒环内完美的分子内碱基互补性。因此，如在电子显微镜中所见，PSTV的刚性、棒状天然二级结构必定基于有缺陷的而非均匀的RNA螺旋。对PSTV中胞苷经亚硫酸氢盐催化修饰为尿苷的详细分析表明，大多数胞苷的反应性高于完美螺旋所预期的反应性。由于已知仅单链区域中的胞苷具有完全反应性，这一发现为PSTV螺旋二级结构中的缺陷提供了额外证据。
