Modulation of pre-mRNA structure by hnRNP proteins regulates alternative splicing of <i>MALT1</i>
Alisha N Jones, Carina Graß, Isabel Meininger, Arie Geerlof, Melina Klostermann, Kathi Zarnack, Daniel Krappmann, Michael Sattler
Abstract
Alternative splicing plays key roles for cell type–specific regulation of protein function. It is controlled by cis-regulatory RNA elements that are recognized by RNA binding proteins (RBPs). The MALT1 paracaspase is a key factor of signaling pathways that mediate innate and adaptive immune responses. Alternative splicing of MALT1 is critical for controlling optimal T cell activation. We demonstrate that MALT1 splicing depends on RNA structural elements that sequester the splice sites of the alternatively spliced exon7. The RBPs hnRNP U and hnRNP L bind competitively to stem-loop RNA structures that involve the 5′ and 3′ splice sites flanking exon7. While hnRNP U stabilizes RNA stem-loop conformations that maintain exon7 skipping, hnRNP L disrupts these RNA elements to facilitate recruitment of the essential splicing factor U2AF2, thereby promoting exon7 inclusion. Our data represent a paradigm for the control of splice site selection by differential RBP binding and modulation of pre-mRNA structure.