title: A genetic screen for suppressors of a mutated 5' splice site identifies factors associated with later steps of spliceosome assembly.
abstract: Many alleles of human disease genes have mutations within splicing consensus sequences that activate cryptic splice sites. In Caenorhabditis elegans, the unc-73(e936) allele has a G-to-U mutation at the first base of the intron downstream of exon 15, which results in an uncoordinated phenotype. This mutation triggers cryptic splicing at the -1 and +23 positions and retains some residual splicing at the mutated wild-type (wt) position. We previously demonstrated that a mutation in sup-39, a U1 snRNA gene, suppresses e936 by increasing splicing at the wt splice site. We report here the results of a suppressor screen in which we identify three proteins that function in cryptic splice site choice. Loss-of-function mutations in the nonessential splicing factor smu-2 suppress e936 uncoordination through changes in splicing. SMU-2 binds SMU-1, and smu-1(RNAi) also leads to suppression of e936. A dominant mutation in the conserved C-terminal domain of the C. elegans homolog of the human tri-snRNP 27K protein, which we have named SNRP-27, suppresses e936 uncoordination through changes in splicing. We propose that SMU-2, SMU-1, and SNRP-27 contribute to the fidelity of splice site choice after the initial identification of 5' splice sites by U1 snRNP.
authors.affiliation: Department of Molecular, Cell, and Developmental Biology and Center for Molecular Biology of RNA, University of California, Santa Cruz, California 95064, USA.
authors.forename: Maryann
authors.initials: M
authors.lastname: Dassah
authors.forename: Sophie
authors.initials: S
authors.lastname: Patzek
authors.forename: Valerie M
authors.initials: VM
authors.lastname: Hunt
authors.forename: Pedro E
authors.initials: PE
authors.lastname: Medina
authors.forename: Alan M
authors.initials: AM
authors.lastname: Zahler
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics / Q000502:physiology; D029742:Caenorhabditis elegans Proteins / Q000235:genetics*; D002874:Chromosome Mapping; D005260:Female; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008969:Molecular Sequence Data; D009043:Motor Activity / Q000235:genetics / Q000502:physiology; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics; D022821:RNA Splice Sites / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000235:genetics; D017411:Ribonucleoproteins, Small Nuclear / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D017381:Spliceosomes / Q000235:genetics*; D013489:Suppression, Genetic
chemical_list: D029742:Caenorhabditis elegans Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D022821:RNA Splice Sites; D012097:Repressor Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear; D017411:Ribonucleoproteins, Small Nuclear; C488500:SMU-2 protein, C elegans; C432686:Smu-1 protein, C elegans; C111263:UNC-73 protein, C elegans