SPLICING IN CAENORHABDITIS-ELEGANS DOES NOT REQUIRE AN AG AT THE 3' SPLICE ACCEPTOR SITE
SPLICING IN CAENORHABDITIS-ELEGANS DOES NOT REQUIRE AN AG AT THE 3' SPLICE ACCEPTOR SITE
复制标题
DOI：
10.1128/mcb.13.1.626
复制
发表时间：
1993-01-01
影响因子：
5.3
通讯作者：
STERNBERG, PW
中科院分区：
文献类型：
--
作者：
AROIAN, RV;LEVY, AD;STERNBERG, PW
二核苷酸AG，发现于几乎所有真核细胞前mRNA内含子的3‘端，被认为是剪接所必需的。秀丽线虫的两个基因，受体酪氨酸激酶基因let-23和胶原基因dpy-10的功能减退突变，都改变了AA的短内含子(约50个核苷酸)末端的AG。通过对从两个突变体中分离的聚合酶链式反应扩增反转录RNA进行测序，研究了这些突变在体内的影响。正如预期的那样，我们发现了剪接到神秘AG的转录本，跳过了一个外显子，并保留了一个未剪接的内含子。然而，我们也发现在突变的3‘剪接点(AA)和附近的非AG二核苷酸存在显著的剪接水平。我们的结果表明，对于线虫内含子来说，无论是正确的3‘剪接位点还是错误的剪接位点，AG都不是剪接所必需的。对一个涉及更长的316个核苷酸的C elegans内含子的剪接位点突变的分析表明，那里也不需要一个AO来进行剪接。我们假设，除了不变AG之外的元件，例如A-U富集区、UUUC基序和/或潜在的分支点序列，正在指导3‘剪接点的选择，并且在野生型基因中，这些元件相互协作，从而发生适当的剪接。
The dinucleotide AG, found at the 3' end of virtually all eukaryotic pre-mRNA introns, is thought to be essential for splicing. Reduction-of-function mutations in two Caenorhabditis elegans genes, the receptor tyrosine kinase gene let-23 and the collagen gene dpy-10, both alter the AG at the end of a short (ca. 50-nucleotide) intron to AA. The in vivo effects of these mutations were studied by sequencing polymerase chain reaction-amplified reverse-transcribed RNA isolated from the two mutants. As expected, we find transcripts that splice to a cryptic AG, skip an exon, and retain an unspliced intron. However, we also find significant levels of splicing at the mutated 3' splice site (AA) and at nearby non-AG dinucleotides. Our results indicate that for short C. elegans introns an AG is not required for splicing at either the correct 3' splice site or incorrect sites. Analysis of a splice site mutant involving a longer, 316-nucleotide C elegans intron indicates that an AO is also not required there for splicing. We hypothesize that elements besides the invariant AG, e.g., an A-U-rich region, a UUUC motif, and/or a potential branch point sequence, are directing the selection of the 3' splice site and that in wild-type genes these elements cooperate so that proper splicing occurs.