title: RNA chaperone activity of L1 ribosomal proteins: phylogenetic conservation and splicing inhibition.
abstract: RNA chaperone activity is defined as the ability of proteins to either prevent RNA from misfolding or to open up misfolded RNA conformations. One-third of all large ribosomal subunit proteins from E. coli display this activity, with L1 exhibiting one of the highest activities. Here, we demonstrate via the use of in vitro trans- and cis-splicing assays that the RNA chaperone activity of L1 is conserved in all three domains of life. However, thermophilic archaeal L1 proteins do not display RNA chaperone activity under the experimental conditions tested here. Furthermore, L1 does not exhibit RNA chaperone activity when in complexes with its cognate rRNA or mRNA substrates. The evolutionary conservation of the RNA chaperone activity among L1 proteins suggests a functional requirement during ribosome assembly, at least in bacteria, mesophilic archaea and eukarya. Surprisingly, rather than facilitating catalysis, the thermophilic archaeal L1 protein from Methanococcus jannaschii (MjaL1) completely inhibits splicing of the group I thymidylate synthase intron from phage T4. Mutational analysis of MjaL1 excludes the possibility that the inhibitory effect is due to stronger RNA binding. To our knowledge, MjaL1 is the first example of a protein that inhibits group I intron splicing.
authors.affiliation: Max F. Perutz Laboratories, Department of Biochemistry, University of Vienna, Dr Bohrgasse 9/5, A-1030 Vienna, Austria.
authors.forename: Stefan L
authors.initials: SL
authors.lastname: Ameres
authors.forename: Dmitry
authors.initials: D
authors.lastname: Shcherbakov
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Nikonova
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Piendl
authors.forename: Renée
authors.initials: R
authors.lastname: Schroeder
authors.forename: Katharina
authors.initials: K
authors.lastname: Semrad
mesh_terms: D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D004252:DNA Mutational Analysis; D029968:Escherichia coli Proteins / Q000378:metabolism; D019143:Evolution, Molecular; D017017:Methanococcus / Q000235:genetics; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012326:RNA Splicing; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism; D012335:RNA, Ribosomal / Q000737:chemistry / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D019843:Archaeal Proteins; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; D012269:Ribosomal Proteins; C028546:ribosomal protein L1