Regulatory mechanisms for 3'-end alternative splicing and polyadenylation of the Glial Fibrillary Acidic Protein, GFAP, transcript.
The glial fibrillary acidic protein, GFAP, forms the intermediate cytoskeleton in cells of the glial lineage. Besides the common GFAP alpha transcript, the GFAP epsilon and GFAP kappa transcripts are generated by alternative mRNA 3'-end processing. Here we use a GFAP minigene to characterize molecular mechanisms participating in alternative GFAP expression. Usage of a polyadenylation signal within the alternatively spliced exon 7a is essential to generate the GFAP kappa and GFAP kappa transcripts. The GFAP kappa mRNA is distinct from GFAP epsilon mRNA given that it also includes intron 7a. Polyadenylation at the exon 7a site is stimulated by the upstream splice site. Moreover, exon 7a splice enhancer motifs supported both exon 7a splicing and polyadenylation. SR proteins increased the usage of the exon 7a polyadenylation signal but not the exon 7a splicing, whereas the polypyrimidine tract binding (PTB) protein enhanced both exon 7a polyadenylation and exon 7a splicing. Finally, increasing transcription by the VP16 trans-activator did not affect the frequency of use of the exon 7a polyadenylation signal whereas the exon 7a splicing frequency was decreased. Our data suggest a model with the selection of the exon 7a polyadenylation site being the essential and primary event for regulating GFAP alternative processing.
Blechingberg
Jenny
J
Institute of Human Genetics, The Bartholin Building, University of Aarhus, DK-8000 Aarhus C, Denmark.
Lykke-Andersen
Søren
S
Jensen
Torben Heick
TH
Jørgensen
Arne Lund
AL
Nielsen
Anders Lade
AL
D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002478:Cells, Cultured; D005091:Exons; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007438:Introns; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D026723:Polyadenylation; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D022821:RNA Splice Sites; D020871:RNA Stability; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D051381:Rats; D000068103:Serine-Arginine Splicing Factors; D014158:Transcription, Genetic
D005904:Glial Fibrillary Acidic Protein; D009687:Nuclear Proteins; D020033:Protein Isoforms; D022821:RNA Splice Sites; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors