Spellman Rachel, Llorian Miriam, Smith Christopher W J
Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, UK.
Mol Cell. 2007 Aug 3;27(3):420-34. doi: 10.1016/j.molcel.2007.06.016.
Among the targets of the repressive splicing regulator, polypyrimidine tract binding protein (PTB) is its own pre-mRNA, where PTB-induced exon 11 skipping produces an RNA substrate for nonsense-mediated decay (NMD). To identify additional PTB-regulated alternative splicing events, we used quantitative proteomic analysis of HeLa cells after knockdown of PTB. Apart from loss of PTB, the only change was upregulation of the neuronally restricted nPTB, resulting from decreased skipping of nPTB exon 10, a splicing event that leads to NMD of nPTB mRNA. Compared with knockdown of PTB alone, simultaneous knockdown of PTB and nPTB led to larger changes in alternative splicing of known and newly identified PTB-regulated splicing events. Strikingly, the hematopoietic PTB paralog ROD1 also switched from a nonproductive splicing pathway upon PTB/nPTB knockdown. Our data indicate crossregulation between PTB and its paralogs via nonproductive alternative splicing and a large degree of functional overlap between PTB and nPTB.
在抑制性剪接调节因子的靶标中，多嘧啶序列结合蛋白（PTB）的自身前体信使核糖核酸（pre-mRNA）就是其靶标之一，PTB诱导的外显子11跳跃会产生一种用于无义介导的mRNA降解（NMD）的RNA底物。为了鉴定其他受PTB调控的可变剪接事件，我们对PTB敲低后的HeLa细胞进行了定量蛋白质组分析。除了PTB缺失外，唯一的变化是神经元特异性的nPTB上调，这是由于nPTB外显子10跳跃减少所致，该剪接事件会导致nPTB mRNA的NMD。与单独敲低PTB相比，同时敲低PTB和nPTB会使已知的以及新鉴定的受PTB调控的剪接事件在可变剪接方面产生更大的变化。引人注目的是，造血系统中的PTB旁系同源物ROD1在PTB/nPTB敲低后也从非生产性剪接途径转变。我们的数据表明，PTB与其旁系同源物之间通过非生产性可变剪接相互交叉调节，并且PTB和nPTB之间存在很大程度的功能重叠。
