U2AF binding selects for the high conservation of the C-elegans 3′ splice site
U2AF binding selects for the high conservation of the C-elegans 3′ splice site
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DOI：
10.1261/rna.7221605
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发表时间：
2005-03-01
期刊：
影响因子：
4.5
通讯作者：
Blumenthal, T
中科院分区：
文献类型：
--
作者：
Hollins, C;Zorio, DAR;Blumenthal, T
秀丽隐杆线虫在动物中是不寻常的，在3'剪接位点具有高度保守的八聚体序列：UUUU CAG/R。该序列可与必需的异源二聚体剪接因子U2 AF结合，其中U2 AF（65）接触U束，U2 AF（35）接触剪接位点本身（AG/R）。在这里，我们证明了一个强大的对应关系与变异八聚体序列的RNA寡核苷酸与U2 AF的结合和这种变化发生在剪接位点的频率。C.秀丽线虫L12 AF对八聚体序列有很强的偏好，并对3 ′剪接位点施加很大的压力以具有精确的UUUUCAG/R序列。在两个位置的剪接位点有一个非常强烈的偏好U，即使替代碱基也可以紧密结合U2 AF，这表明进化可以选择对序列，可能有一个相对温和的减少结合。虽然嘧啶经常出现在外显子的第一个碱基上，但U2 AF对它们有很强的偏好，认为存在一种机制来补偿U2 AF在该位置的结合减弱。最后，共有序列中的C必须保持与AG/R相邻，而不是与U的延伸相邻，这表明该C被U2 AF识别（35）。
Caenorhabditis elegans is unusual among animals in having a highly conserved octamer sequence at the 3' splice site: UUUU CAG/R. This sequence can bind to the essential heterodimeric splicing factor U2AF, with U2AF(65) contacting the U tract and U2AF(35) contacting the splice site itself (AG/R). Here we demonstrate a strong correspondence between binding to U2AF of RNA oligonucleotides with variant octamer sequences and the frequency with which such variations occur in splice sites. C. elegans L12AF has a strong preference for the octamer sequence and exerts much of the pressure for 3' splice sites to have the precise UUUUCAG/R sequence. At two positions the splice site has a very strong preference for U even though alternative bases can also bind tightly to U2AF, suggesting that evolution can select against sequences that may have a relatively modest reduction in binding. Although pyrimidines are frequently present at the first base in the exon, U2AF has a very strong bias against them, arguing there is a mechanism to compensate for weakened U2AF binding at this position. Finally, the C in the consensus sequence must remain adjacent to the AG/R rather than to the stretch of U's, suggesting this C is recognized by U2AF(35).