title: hnRNP A1 and secondary structure coordinate alternative splicing of Mag.
abstract: Myelin-associated glycoprotein (MAG) is a major component of myelin in the vertebrate central nervous system. MAG is present in the periaxonal region of the myelin structure, where it interacts with neuronal proteins to inhibit axon outgrowth and protect neurons from degeneration. Two alternatively spliced isoforms of Mag mRNA have been identified. The mRNA encoding the shorter isoform, known as S-MAG, contains a termination codon in exon 12, while the mRNA encoding the longer isoform, known as L-MAG, skips exon 12 and produces a protein with a longer C-terminal region. L-MAG is required in the central nervous system. How inclusion of Mag exon 12 is regulated is not clear. In a previous study, we showed that heteronuclear ribonucleoprotein A1 (hnRNP A1) contributes to Mag exon 12 skipping. Here, we show that hnRNP A1 interacts with an element that overlaps the 5' splice site of Mag exon 12. The element has a reduced ability to interact with the U1 snRNP compared with a mutant that improves the splice site consensus. An evolutionarily conserved secondary structure is present surrounding the element. The structure modulates interaction with both hnRNP A1 and U1. Analysis of splice isoforms produced from a series of reporter constructs demonstrates that the hnRNP A1-binding site and the secondary structure both contribute to exclusion of Mag exon 12.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
authors.forename: N Ruth
authors.initials: NR
authors.lastname: Zearfoss
authors.forename: Emily S
authors.initials: ES
authors.lastname: Johnson
authors.forename: Sean P
authors.initials: SP
authors.lastname: Ryder
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D001665:Binding Sites; D045744:Cell Line, Tumor; D005091:Exons; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000235:genetics / Q000378:metabolism*; D055029:Inverted Repeat Sequences; D051379:Mice; D018992:Myelin-Associated Glycoprotein / Q000235:genetics / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D025941:Protein Interaction Mapping; D059368:RNA Isoforms / Q000235:genetics / Q000378:metabolism; D022821:RNA Splice Sites; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D017381:Spliceosomes / Q000235:genetics / Q000378:metabolism
chemical_list: D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; C104739:Mag protein, mouse; D018992:Myelin-Associated Glycoprotein; D059368:RNA Isoforms; D022821:RNA Splice Sites; D012333:RNA, Messenger
keywords: Mag; alternative splicing; hnRNP A1; myelin; myelin-associated glycoprotein; secondary structure