Jeeninga R E, Van Delft Y, de Graaff-Vincent M, Dirks-Mulder A, Venema J, Raué H A
Department of Biochemistry & Molecular Biology, IMBW, BioCentrum Amsterdam, Vrije Universiteit De Boelelaan, The Netherlands.
RNA. 1997 May;3(5):476-88.
The homologous ribosomal RNA species of all organisms can be folded into a common "core" secondary structure. In addition, eukaryotic rRNAs contain a large number of segments, located at fixed positions, that are highly variable in size and sequence from one organism to another. We have investigated the role of the two largest of these variable regions in Saccharomyces cerevisiae 25S rRNA, V13, and V3, by mutational analysis in a yeast strain that can be rendered completely dependent on the synthesis of mutant (pre-)rRNA. We found that approximately half of variable region V13 can be deleted without any phenotypic effect. The remaining portion, however, contains multiple structural features whose disturbance causes serious growth defects or lethality. Accumulation of 25S rRNA is strongly reduced by these mutations, at least in part because they inhibit processing of ITS2. Removal of even a relatively small portion of V3 also strongly reduces the cellular growth rate and larger deletions are lethal. Interestingly, some of the deletions in V3 cause accumulation of 27S(A) pre-rRNA and, moreover, appear to interfere with the close coupling between the processing cleavages at sites A3 and B1(S). These results demonstrate that both variable regions play an important role in 60S subunit formation.
所有生物体的同源核糖体RNA种类都可以折叠成一种共同的“核心”二级结构。此外，真核生物的rRNA包含大量位于固定位置的片段，这些片段在不同生物体之间的大小和序列高度可变。我们通过在一种可以完全依赖突变（前体）rRNA合成的酵母菌株中进行突变分析，研究了酿酒酵母25S rRNA中两个最大的可变区域V13和V3的作用。我们发现，可变区域V13的大约一半可以被删除而不产生任何表型效应。然而，其余部分包含多个结构特征，其干扰会导致严重的生长缺陷或致死性。这些突变会强烈降低25S rRNA的积累，至少部分原因是它们抑制了ITS2的加工。即使去除V3中相对较小的一部分也会强烈降低细胞生长速率，更大的缺失则是致死的。有趣的是，V3中的一些缺失会导致27S(A)前体rRNA的积累，而且似乎会干扰A3和B1(S)位点加工切割之间的紧密偶联。这些结果表明，这两个可变区域在60S亚基形成中都起着重要作用。
