Auto- and cross-regulation of the hnRNP L proteins by alternative splicing.
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.
Rossbach
Oliver
O
Institute of Biochemistry, Justus-Liebig-University of Giessen, Giessen, Germany.
Hung
Lee-Hsueh
LH
Schreiner
Silke
S
Grishina
Inna
I
Heiner
Monika
M
Hui
Jingyi
J
Bindereif
Albrecht
A
D017398:Alternative Splicing; D004742:Enhancer Elements, Genetic; D005091:Exons; D005786:Gene Expression Regulation; D006367:HeLa Cells; D034664:Heterogeneous-Nuclear Ribonucleoprotein L / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D007438:Introns; D009690:Nucleic Acid Conformation; D012322:RNA Precursors / Q000096:biosynthesis / Q000235:genetics
D034664:Heterogeneous-Nuclear Ribonucleoprotein L; D012322:RNA Precursors