Morrison M, Harris K S, Roth M B
Molecular and Cellular Biology Program, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue, Seattle, WA 98105, USA.
Proc Natl Acad Sci U S A. 1997 Sep 2;94(18):9782-5. doi: 10.1073/pnas.94.18.9782.
The expression of alternatively spliced mRNAs from genes is an ubiquitous phenomenon in metazoa. A screen for trans-acting factors that alter the expression of alternatively spliced mRNAs reveals that the smg genes of Caenorhabditis elegans participate in this process. smg genes have been proposed to function in degradation of nonsense mutant mRNAs. Here we show that smg genes affect normal gene expression by modulating the levels of alternatively spliced SRp20 and SRp30b mRNAs. These SR genes contain alternatively spliced exons that introduce upstream stop codons. The effect of smg genes on SR transcripts is specific, because the gene encoding the catalytic subunit of the cAMP-dependent protein kinase, which also contains an alternatively spliced exon that introduces upstream stop codon, is not effected in a smg background. These results suggest that the levels of alternatively spliced mRNAs may, in part, be regulated by alternative mRNA stability.
基因可变剪接mRNA的表达是后生动物中普遍存在的现象。一项针对改变可变剪接mRNA表达的反式作用因子的筛选显示，秀丽隐杆线虫的smg基因参与了这一过程。有人提出smg基因在无义突变mRNA的降解中发挥作用。在这里，我们表明smg基因通过调节可变剪接的SRp20和SRp30b mRNA的水平来影响正常基因表达。这些SR基因包含可变剪接的外显子，这些外显子引入上游终止密码子。smg基因对SR转录本的影响是特异性的，因为编码cAMP依赖性蛋白激酶催化亚基的基因也包含一个引入上游终止密码子的可变剪接外显子，在smg背景下不受影响。这些结果表明，可变剪接mRNA的水平可能部分受mRNA稳定性的调节。
