title: A pyrimidine-rich exonic splicing suppressor binds multiple RNA splicing factors and inhibits spliceosome assembly.
abstract: The bovine papillomavirus type 1 (BPV-1) exonic splicing suppressor (ESS) is juxtaposed immediately downstream of BPV-1 splicing enhancer 1 and negatively modulates selection of a suboptimal 3' splice site at nucleotide 3225. The present study demonstrates that this pyrimidine-rich ESS inhibits utilization of upstream 3' splice sites by blocking early steps in spliceosome assembly. Analysis of the proteins that bind to the ESS showed that the U-rich 5' region binds U2AF65 and polypyrimidine tract binding protein, the C-rich central part binds 35- and 54-55-kDa serine/arginine-rich (SR) proteins, and the AG-rich 3' end binds alternative splicing factor/splicing factor 2. Mutational and functional studies indicated that the most critical region of the ESS maps to the central C-rich core (GGCUCCCCC). This core sequence, along with additional nonspecific downstream nucleotides, is sufficient for partial suppression of spliceosome assembly and splicing of BPV-1 pre-mRNAs. The inhibition of splicing by the ESS can be partially relieved by excess purified HeLa SR proteins, suggesting that the ESS suppresses pre-mRNA splicing by interfering with normal bridging and recruitment activities of SR proteins.
authors.affiliation: Basic Research Laboratory, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Building 41, Room D305, Bethesda, MD 20892-5055, USA. zheng@dce41.nci.nih.gov
authors.forename: Z M
authors.initials: ZM
authors.lastname: Zheng
authors.forename: M
authors.initials: M
authors.lastname: Huynen
authors.forename: C C
authors.initials: CC
authors.lastname: Baker
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D052688:Bovine papillomavirus 1 / Q000235:genetics* / Q000378:metabolism; D002417:Cattle; D004742:Enhancer Elements, Genetic; D005091:Exons; D015497:HIV-1 / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000378:metabolism; D009690:Nucleic Acid Conformation; D016133:Polymerase Chain Reaction; D012322:RNA Precursors / Q000737:chemistry / Q000235:genetics; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics; D016601:RNA-Binding Proteins; D017384:Sequence Deletion; D000068103:Serine-Arginine Splicing Factors; D017381:Spliceosomes / Q000235:genetics / Q000378:metabolism; D013698:Templates, Genetic; D014158:Transcription, Genetic
chemical_list: D009687:Nuclear Proteins; D012322:RNA Precursors; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors