Xiao Xinshu, Wang Zefeng, Jang Minyoung, Nutiu Razvan, Wang Eric T, Burge Christopher B
Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
Nat Struct Mol Biol. 2009 Oct;16(10):1094-100. doi: 10.1038/nsmb.1661. Epub 2009 Sep 13.
Pre-mRNA splicing is regulated through the combinatorial activity of RNA motifs, including splice sites and splicing regulatory elements. Here we show that the activity of the G-run (polyguanine sequence) class of splicing enhancer elements is approximately 4-fold higher when adjacent to intermediate strength 5' splice sites (ss) than when adjacent to weak 5' ss, and approximately 1.3-fold higher relative to strong 5' ss. We observed this dependence on 5' ss strength in both splicing reporters and in global microarray and mRNA-Seq analyses of splicing changes following RNA interference against heterogeneous nuclear ribonucleoprotein (hnRNP) H, which cross-linked to G-runs adjacent to many regulated exons. An exon's responsiveness to changes in hnRNP H levels therefore depends in a complex way on G-run abundance and 5' ss strength. This pattern of activity enables G-runs and hnRNP H to buffer the effects of 5' ss mutations, augmenting both the frequency of 5' ss polymorphism and the evolution of new splicing patterns. Certain other splicing factors may function similarly.
前体mRNA剪接是通过RNA基序（包括剪接位点和剪接调控元件）的组合活性来调控的。我们在此表明，剪接增强子元件的G序列（聚鸟嘌呤序列）类的活性，在与中等强度的5'剪接位点（ss）相邻时，比与弱5' ss相邻时高约4倍，相对于强5' ss高约1.3倍。我们在剪接报告基因以及对异质性核核糖核蛋白（hnRNP）H进行RNA干扰后剪接变化的全基因组微阵列和mRNA测序分析中都观察到了这种对5' ss强度的依赖性，hnRNP H与许多受调控外显子相邻的G序列交联。因此，一个外显子对hnRNP H水平变化的反应性以复杂的方式取决于G序列丰度和5' ss强度。这种活性模式使G序列和hnRNP H能够缓冲5' ss突变的影响，增加5' ss多态性的频率和新剪接模式的演变。某些其他剪接因子可能也有类似的功能。
