Auto- and Cross-Regulation of the hnRNP L Proteins by Alternative Splicing
Auto- and Cross-Regulation of the hnRNP L Proteins by Alternative Splicing
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通过选择性剪接对 hnRNP L 蛋白进行自动和交叉调节
DOI：
10.1128/mcb.01689-08
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发表时间：
2009-03-15
影响因子：
5.3
通讯作者：
Bindereif, Albrecht
中科院分区：
文献类型：
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作者：
Rossbach, Oliver;Hung, Lee-Hsueh;Bindereif, Albrecht
我们最近将人hnRNP L鉴定为选择性剪接的全局调节因子，与CA重复序列和富含CA的元件结合。在这里，我们报告说，hnRNP L自动调节其自身的表达水平上的选择性剪接。人hnRNP L基因的内含子6含有一个短的外显子，如果使用该外显子，则引入提前终止密码子，导致无义介导的衰变（NMD）。这个“毒外显子”之前是一个高度保守的富含CA的簇，其延伸超过800个核苷酸，结合hnRNP L，并作为一个异常延伸的内含子增强子发挥作用，促进包含毒外显子。因此，过量的hnRNP L激活其自身mRNA的NMD，从而产生负的自动调节反馈环并有助于hnRNP L水平的稳态。我们目前的实验证据表明，这种机制的基础上，NMD灭活，hnRNP L结合试验，和hnRNP L依赖的选择性剪接的异源构建体。此外，我们表明，hnRNP L交叉调节列入一个类似的毒药外显子的hnRNP L样前mRNA，这解释了两个密切相关的hnRNP L蛋白的相互表达。
ABSTRACT We recently characterized human hnRNP L as a global regulator of alternative splicing, binding to CA-repeat and CA-rich elements. Here we report that hnRNP L autoregulates its own expression on the level of alternative splicing. Intron 6 of the human hnRNP L gene contains a short exon that, if used, introduces a premature termination codon, resulting in nonsense-mediated decay (NMD). This “poison exon” is preceded by a highly conserved CA-rich cluster extending over 800 nucleotides that binds hnRNP L and functions as an unusually extended, intronic enhancer, promoting inclusion of the poison exon. As a result, excess hnRNP L activates NMD of its own mRNA, thereby creating a negative autoregulatory feedback loop and contributing to homeostasis of hnRNP L levels. We present experimental evidence for this mechanism, based on NMD inactivation, hnRNP L binding assays, and hnRNP L-dependent alternative splicing of heterologous constructs. In addition, we demonstrate that hnRNP L cross-regulates inclusion of an analogous poison exon in the hnRNP L-like pre-mRNA, which explains the reciprocal expression of the two closely related hnRNP L proteins.