51. Auto- and Cross-Regulation of the hnRNP L Proteins by Alternative Splicing.
- Author
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Rossbach, Oliver, Lee-Hsueh Hung, Schreiner, Silke, Grishina, Inna, Heiner, Monika, Jingyi Hui, and Bindereif, Albrecht
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GENES ,MESSENGER RNA ,HOMEOSTASIS ,EXONS (Genetics) ,PROTEINS - 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. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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