HnRNP L represses exon splicing via a regulated exonic splicing silencer.
Skipping of mammalian exons during pre-mRNA splicing is commonly mediated by the activity of exonic splicing silencers (ESSs). We have recently identified a regulated ESS within variable exon 4 of the CD45 gene, named ESS1, that is necessary and sufficient for partial exon repression in resting T cells and has additional silencing activity upon T-cell activation. In this study, we identify three heterogeneous nuclear ribonucleoproteins (hnRNPs) that bind specifically to ESS1. The binding of one of these proteins, hnRNP-L, is significantly decreased by mutations that disrupt both the basal and induced activities of ESS1. Recombinant hnRNP-L functions to repress exon inclusion in vitro in an ESS1-dependent manner. Moreover, depletion of hnRNP-L, either in vitro or in vivo, leads to increased exon inclusion. In contrast, the other ESS1-binding proteins, PTB and hnRNP E2, do not discriminate between wild-type and mutant ESS1 in binding studies, and do not specifically alter ESS1-dependent splicing in vitro. Together, these studies demonstrate that hnRNP-L is the primary protein through which CD45 exon 4 silencing is mediated by the regulatory sequence ESS1.
Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA.
Caryn R
CR
Rothrock
Amy E
AE
House
Kristen W
KW
Lynch
D000818:Animals; D001483:Base Sequence; D005091:Exons / Q000502:physiology*; D034664:Heterogeneous-Nuclear Ribonucleoprotein L / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D017493:Leukocyte Common Antigens / Q000235:genetics; D008969:Molecular Sequence Data; D038941:Polypyrimidine Tract-Binding Protein / Q000378:metabolism; D012326:RNA Splicing / Q000502:physiology*; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology; D037941:Silencer Elements, Transcriptional / Q000502:physiology*
D034664:Heterogeneous-Nuclear Ribonucleoprotein L; D012097:Repressor Proteins; D038941:Polypyrimidine Tract-Binding Protein; D017493:Leukocyte Common Antigens