Exon selection in alpha-tropomyosin mRNA is regulated by the antagonistic action of RBM4 and PTB.
RNA-binding motif protein 4 (RBM4) has been implicated in the regulation of precursor mRNA splicing. Using differential display analysis, we identified mRNAs that associate with RBM4-containing messenger RNPs in vivo. Among these mRNAs, alpha-tropomyosin (alpha-TM) is known to exhibit a muscle cell type-specific splicing pattern. The level of the skeletal muscle-specific alpha-TM mRNA isoform partially correlated with that of RBM4 in human tissues examined and could be modulated by ectopic overexpression or suppression of RBM4. These results indicated that RBM4 directly influences the expression of the skeletal muscle-specific alpha-TM isoform. Using minigenes, we demonstrated that RBM4 can activate the selection of skeletal muscle-specific exons, possibly via binding to intronic pyrimidine-rich elements. By contrast, the splicing regulator polypyrimidine tract binding protein (PTB) excluded these exons; moreover, RBM4 antagonized this PTB-mediated exon exclusion likely by competing with PTB for binding to a CU-rich element. This study suggests a possible mechanism underlying the regulated alternative splicing of alpha-TM by the antagonistic splicing regulators RBM4 and PTB.
Lin
Jung-Chun
JC
Institute of Biomedical Sciences, Academia Sinica, 128 Academy Road Section 2, Nankang, Taipei 11529, Taiwan.
Tarn
Woan-Yuh
WY
D017398:Alternative Splicing; D015152:Blotting, Northern; D002460:Cell Line; D017931:DNA Primers / Q000737:chemistry; D005091:Exons; D020869:Gene Expression Profiling; D006801:Humans; D007438:Introns; D008954:Models, Biological; D008957:Models, Genetic; D018482:Muscle, Skeletal / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D016133:Polymerase Chain Reaction; D038941:Polypyrimidine Tract-Binding Protein / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D020033:Protein Isoforms; D011743:Pyrimidines / Q000737:chemistry; D012313:RNA / Q000737:chemistry; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014018:Tissue Distribution; D014335:Tropomyosin / Q000235:genetics* / Q000378:metabolism
D017931:DNA Primers; D020033:Protein Isoforms; D011743:Pyrimidines; C473692:RBM4 protein, human; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D014335:Tropomyosin; D038941:Polypyrimidine Tract-Binding Protein; D012313:RNA; C030986:pyrimidine