The CELF family of RNA binding proteins is implicated in cell-specific and developmentally regulated alternative splicing.
Alternative splicing of cardiac troponin T (cTNT) exon 5 undergoes a developmentally regulated switch such that exon inclusion predominates in embryonic, but not adult, striated muscle. We previously described four muscle-specific splicing enhancers (MSEs) within introns flanking exon 5 in chicken cTNT that are both necessary and sufficient for exon inclusion in embryonic muscle. We also demonstrated that CUG-binding protein (CUG-BP) binds a conserved CUG motif within a human cTNT MSE and positively regulates MSE-dependent exon inclusion. Here we report that CUG-BP is one of a novel family of developmentally regulated RNA binding proteins that includes embryonically lethal abnormal vision-type RNA binding protein 3 (ETR-3). This family, which we call CELF proteins for CUG-BP- and ETR-3-like factors, specifically bound MSE-containing RNAs in vitro and activated MSE-dependent exon inclusion of cTNT minigenes in vivo. The expression of two CELF proteins is highly restricted to brain. CUG-BP, ETR-3, and CELF4 are more broadly expressed, and expression is developmentally regulated in striated muscle and brain. Changes in the level of expression and isoforms of ETR-3 in two different developmental systems correlated with regulated changes in cTNT splicing. A switch from cTNT exon skipping to inclusion tightly correlated with induction of ETR-3 protein expression during differentiation of C2C12 myoblasts. During heart development, the switch in cTNT splicing correlated with a transition in ETR-3 protein isoforms. We propose that ETR-3 is a major regulator of cTNT alternative splicing and that the CELF family plays an important regulatory role in cell-specific alternative splicing during normal development and disease.
Ladd
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Department of Pathology, Baylor College of Medicine, Houston, Texas 77030, USA.
Charlet
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Cooper
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D000328:Adult; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000254:growth & development / Q000378:metabolism; D000067878:CELF Proteins; D000067879:CELF1 Protein; D002460:Cell Line; D002645:Chickens; D017931:DNA Primers / Q000235:genetics; D004742:Enhancer Elements, Genetic; D005091:Exons; D005260:Female; D015870:Gene Expression; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D024510:Muscle Development; D018482:Muscle, Skeletal / Q000254:growth & development / Q000378:metabolism; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D020107:Troponin T / Q000235:genetics
D000067878:CELF Proteins; D000067879:CELF1 Protein; C102843:CELF1 protein, human; C117363:CELF2 protein, human; C422242:CELF3 protein, human; C422243:CELF4 protein, human; C422244:CELF5 protein, human; D017931:DNA Primers; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D020107:Troponin T