title: SF2/ASF binds to a splicing enhancer in the third HIV-1 tat exon and stimulates U2AF binding independently of the RS domain.
abstract: Splicing of a single HIV-1 primary transcript into more than 30 different mRNAs is regulated by a combination of suboptimal splice sites, cis-acting RNA splicing enhancers and silencers, and trans-acting factors. We have studied the splicing of the second tat intron (SD4 to SA7) and find that activation of splicing by SF2/ASF is mediated by a degenerate exon splicing enhancer (ESE3), consisting of at least three functionally independent sub-elements. One of these sub-elements appears to have both enhancing and silencing properties, depending on the context. SF2/ASF stimulates U2AF65 binding to the suboptimal tat polypyrimidine tract in an ESE3-dependent manner, whereas the exon splicing silencer (ESS3) that is located downstream of the ESE3 inhibits this step. Truncated SF2/ASF protein without the RS domain binds specifically to the ESE3 and retains almost full capacity to stimulate U2AF65 binding and activate splicing. This suggests that SF2/ASF can stimulate the recruitment of U2AF65 by an RS domain-independent mechanism.
authors.affiliation: Department of Molecular and Structural Biology, University of Aarhus, C.F. Møllers Allé Building 130, DK-8000 Arhus C, Denmark.
authors.forename: T Ø
authors.initials: TØ
authors.lastname: Tange
authors.forename: J
authors.initials: J
authors.lastname: Kjems
mesh_terms: D001483:Base Sequence; D005091:Exons / Q000235:genetics*; D015696:Gene Products, tat / Q000235:genetics*; D020868:Gene Silencing; D015497:HIV-1 / Q000235:genetics*; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012326:RNA Splicing / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D012261:Ribonucleoproteins / Q000378:metabolism*; D000068103:Serine-Arginine Splicing Factors; D000072668:Splicing Factor U2AF; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D015696:Gene Products, tat; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D000072668:Splicing Factor U2AF; C000607494:U2AF2 protein, human; D054322:tat Gene Products, Human Immunodeficiency Virus; D000068103:Serine-Arginine Splicing Factors