Tounekti N, Mougel M, Roy C, Marquet R, Darlix J L, Paoletti J, Ehresmann B, Ehresmann C
Unité de Biochimie, URA 158 CNRS, Institut Gustave Roussy, Villejuif, France.
J Mol Biol. 1992 Jan 5;223(1):205-20. doi: 10.1016/0022-2836(92)90726-z.
In Moloney murine leukemia virus, the encapsidation Psi element was shown to be necessary and sufficient to promote packaging of viral RNA, and to be required for dimerization. The conformation of the Psi domain (nucleotides 215 to 565) was investigated in solution by chemical probing. The four bases were monitored at one of their Watson-Crick positions with dimethylsulfate at cytosine N3 and adenosine N1, and with a carbodiimide derivative at guanosine N1 and uridine N3. Position N7 of adenine residues was probed with diethylpyrocarbonate. The analyses were conducted on in vitro transcribed fragments corresponding either to the isolated Psi domain or to the 5'-terminal 725 nucleotides. The RNA fragments were analyzed in their monomeric and dimeric forms. A secondary structure model was derived from probing data, computer prediction and sequence analysis of related murine retroviruses. One major result is that Psi forms an independent and highly structured domain. Dimerization induces an extensive reduction of reactivity in region 278 to 309 that can be interpreted as the result of intermolecular interactions and/or intramolecular conformational rearrangements. A second region (around position 215) was shown to display discrete reactivity changes upon dimerization. These two regions represent likely elements of dimerization. More unexpectedly, reactivity changes (essentially enhancement of reactivity) were also detected in another part of Psi (around position 480) not believed to contain elements of dimerization. These reactivity changes could be interpreted as dimerization-induced allosteric transitions.
在莫洛尼鼠白血病病毒中，衣壳化的ψ元件被证明对于促进病毒RNA的包装是必要且充分的，并且是二聚化所必需的。通过化学探针研究了ψ结构域（核苷酸215至565）在溶液中的构象。使用硫酸二甲酯在胞嘧啶N3和腺苷N1处、碳二亚胺衍生物在鸟苷N1和尿苷N3处监测四个碱基的一个沃森-克里克位置。用焦碳酸二乙酯探测腺嘌呤残基的N7位置。分析是在体外转录的片段上进行的，这些片段对应于分离的ψ结构域或5'末端的725个核苷酸。对RNA片段的单体和二聚体形式进行了分析。从探测数据、计算机预测以及相关鼠逆转录病毒的序列分析中得出了一个二级结构模型。一个主要结果是ψ形成了一个独立且高度结构化的结构域。二聚化导致278至309区域的反应性大幅降低，这可以解释为分子间相互作用和/或分子内构象重排的结果。第二个区域（约215位附近）在二聚化时显示出离散的反应性变化。这两个区域代表了可能的二聚化元件。更出乎意料的是，在ψ的另一部分（约480位附近）也检测到了反应性变化（主要是反应性增强），该区域被认为不包含二聚化元件。这些反应性变化可以解释为二聚化诱导的变构转变。
