title: The neurospora CYT-18 protein suppresses defects in the phage T4 td intron by stabilizing the catalytically active structure of the intron core.
abstract: The Neurospora CYT-18 protein, a tyrosyl-tRNA synthetase, which functions in splicing group I introns in mitochondria, promotes splicing of mutants of the distantly related bacteriophage T4 td intron. In an in vivo assay, wild-type CYT-18 protein expressed in E. coli suppressed mutations in the td intron's catalytic core. CYT-18-suppressible mutations were also suppressed by high Mg2+ or spermidine in vitro, suggesting they affect intron structure. Both the N- and C-terminal domains of CYT-18 are required for efficient splicing, but CYT-18 with a large C-terminal truncation retains some activity. Our results indicate that CYT-18 interacts with conserved structural features of group I introns, and they provide direct evidence that a protein promotes splicing by stabilizing the catalytically active structure of the intron RNA.
authors.affiliation: Department of Molecular Genetics, Ohio State University, Columbus 43210.
authors.forename: G
authors.initials: G
authors.lastname: Mohr
authors.forename: A
authors.initials: A
authors.lastname: Zhang
authors.forename: J A
authors.initials: JA
authors.lastname: Gianelos
authors.forename: M
authors.initials: M
authors.lastname: Belfort
authors.forename: A M
authors.initials: AM
authors.lastname: Lambowitz
mesh_terms: D001483:Base Sequence; D005656:Fungal Proteins / Q000235:genetics*; D016153:Genes, Suppressor; D005814:Genes, Viral; D007438:Introns; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009492:Neurospora crassa / Q000235:genetics*; D012326:RNA Splicing / Q000187:drug effects; D012367:RNA, Viral / Q000235:genetics; D013095:Spermidine / Q000494:pharmacology; D013604:T-Phages / Q000235:genetics*; D014448:Tyrosine-tRNA Ligase / Q000235:genetics*; D015678:Viral Structural Proteins / Q000235:genetics
chemical_list: D005656:Fungal Proteins; D012367:RNA, Viral; D015678:Viral Structural Proteins; D014448:Tyrosine-tRNA Ligase; D013095:Spermidine