title: Raa4 is a trans-splicing factor that specifically binds chloroplast tscA intron RNA.
abstract: During trans-splicing of discontinuous organellar introns, independently transcribed coding sequences are joined together to generate a continuous mRNA. The chloroplast psaA gene from Chlamydomonas reinhardtii encoding the P(700) core protein of photosystem I (PSI) is split into three exons and two group IIB introns, which are both spliced in trans. Using forward genetics, we isolated a novel PSI mutant, raa4, with a defect in trans-splicing of the first intron. Complementation analysis identified the affected gene encoding the 112.4 kDa Raa4 protein, which shares no strong sequence identity with other known proteins. The chloroplast localization of the protein was confirmed by confocal fluorescence microscopy, using a GFP-tagged Raa4 fusion protein. RNA-binding studies showed that Raa4 binds specifically to domains D2 and D3, but not to other conserved domains of the tripartite group II intron. Raa4 may play a role in stabilizing folding intermediates or functionally active structures of the split intron RNA.
authors.affiliation: Department for General and Molecular Botany, Ruhr-University Bochum, D-44780 Bochum, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Glanz
authors.forename: Jessica
authors.initials: J
authors.lastname: Jacobs
authors.forename: Vera
authors.initials: V
authors.lastname: Kock
authors.forename: Arti
authors.initials: A
authors.lastname: Mishra
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kück
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000235:genetics*; D060365:Chloroplast Proteins / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D007438:Introns; D009154:Mutation; D009690:Nucleic Acid Conformation; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018747:RNA, Chloroplast / Q000235:genetics*; D018749:RNA, Plant / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020040:Trans-Splicing
chemical_list: D060365:Chloroplast Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D018747:RNA, Chloroplast; D018749:RNA, Plant; D016601:RNA-Binding Proteins