Multiple functions for the invariant AGC triad of U6 snRNA
Multiple functions for the invariant AGC triad of U6 snRNA
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DOI：
10.1261/rna.7310704
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发表时间：
2004-06-01
期刊：
影响因子：
4.5
通讯作者：
Staley, JP
中科院分区：
文献类型：
--
作者：
Hilliker, AK;Staley, JP
U6 snRNA的不变AGC三联体在剪接中起着重要的，未知的作用。该三联体与U2、U4和U6中的残基有碱基配对关系。通过对酿酒酵母的遗传分析，我们发现大多数AGC突变体通过恢复与U2的配对来抑制，支持U2/U6螺旋lb的重要性，并通过破坏U2茎I，表明该茎调节螺旋lb的形成。有趣的是，其中一个螺旋lb碱基对是外显子连接所必需的，这增加了整个螺旋lb仅在外显子连接所必需的可能性。我们还发现，U4茎I中减少互补性的U4突变增强了U2介导的AGC突变体的抑制，这表明U4茎I与含有AGC的U4/U6茎I竞争，这意味着三联体的一个额外的基本功能，三个三联体突变体难以抑制，即使同时恢复与U2、U4和U6的配对。在三联体的中心位置对嘌呤的绝对要求与II族内含子中具有重要催化作用的AGC三联体的同等要求是一致的，这与U6的AGC三联体在催化中的作用是一致的。
The invariant AGC triad of U6 snRNA plays an essential, unknown role in splicing. The triad has been implicated in base-pairing with residues in U2, U4, and U6. Through a genetic analysis in S. cerevisiae, we found that most AGC mutants are suppressed both by restoring pairing with U2, supporting the significance of U2/U6 helix lb, and by destabilizing U2 stem I, indicating that this stem regulates helix lb formation. Intriguingly, one of the helix lb base pairs is required specifically for exon ligation, raising the possibility that the entirety of helix lb is required only for exon ligation. We also found that U4 mutations that reduce complementarity in U4 stem I enhance U2-mediated suppression of an AGC mutant, suggesting that U4 stem I competes with the AGC-containing U4/U6 stem I. Implicating an additional, essential function for the triad, three triad Mutants are refractory to suppression-even by simultaneous restoration of pairing with U2, U4, and U6. An absolute requirement for a purine at the central position of the triad parallels an equivalent requirement in a catalytically important AGC triad in group II introns, consistent with a role for the AGC triad of U6 in catalysis.