Patel Abhijit A, McCarthy Matthew, Steitz Joan A
Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06536, USA.
EMBO J. 2002 Jul 15;21(14):3804-15. doi: 10.1093/emboj/cdf297.
Some protein-coding genes in metazoan genomes contain a minor class of introns that are excised by a distinct, low-abundance spliceosome. We have developed a quantitative RT-PCR assay that allows comparison of the relative rates of intron removal from the transcripts present in a pre-mRNA population. We show that the U12-type introns are more slowly spliced than the major-class (U2-type) introns from three endogenous pre-mRNAs in human tissue culture cells. In Drosophila melanogaster S2 cells, using minigene constructs designed to produce nearly identical mRNAs, we observe increased expression of fluorescent protein and mature mRNA upon mutation of a U12-type to a U2-type intron. These results provide evidence that the level of gene expression in vivo is lowered by the presence of a U12-type intron and implicate the U12-type spliceosome as a target in the post-transcriptional regulation of gene expression.
后生动物基因组中的一些蛋白质编码基因含有一小类内含子，这些内含子由一种独特的、低丰度的剪接体切除。我们开发了一种定量逆转录聚合酶链反应检测方法，该方法可以比较从前体mRNA群体中存在的转录本中去除内含子的相对速率。我们发现，在人类组织培养细胞中，U12型内含子的剪接速度比来自三种内源性前体mRNA的主要类型（U2型）内含子更慢。在果蝇S2细胞中，使用设计用于产生几乎相同mRNA的小基因构建体，我们观察到将U12型内含子突变为U2型内含子后，荧光蛋白和成熟mRNA的表达增加。这些结果提供了证据，证明体内基因表达水平因U12型内含子的存在而降低，并表明U12型剪接体是基因表达转录后调控的一个靶点。
