title: A DEAD box protein is required for formation of a hidden break in Arabidopsis chloroplast 23S rRNA.
abstract: In plant chloroplasts, the ribosomal RNA (rRNA) of the large subunit of the ribosome undergoes post-maturation fragmentation processing. This processing consists of site-specific cleavage that generates gapped, discontinuous rRNA molecules. However, the molecular mechanism underlying introduction of the gap structure (the 'hidden break') is poorly understood. Here, we found that the DEAD box protein RH39 plays a key role in introduction of the hidden break into the 23S rRNA in Arabidopsis chloroplasts. Genetic screening for an Arabidopsis plant with a drastically reduced level of ribulose-1,5-bisphosphate carboxylase/oxygenase identified an RH39 mutant. The levels of other chloroplast-encoded photosynthetic proteins were also severely reduced. The reductions were not due to a failure of transcription, but rather inefficiency in translation. RNA gel blotting revealed incomplete fragmentation of 23S rRNA in chloroplasts during maturation. In vitro analysis with recombinant RH39 suggested that the protein binds to the adjacent sequence upstream of the hidden break site to exert its function. We propose a molecular mechanism for the RH39-mediated fragmentation processing of 23S rRNA in chloroplasts.
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Nishimura
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ashida
authors.forename: Taro
authors.initials: T
authors.lastname: Ogawa
authors.forename: Akiho
authors.initials: A
authors.lastname: Yokota
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D015152:Blotting, Northern; D015153:Blotting, Western; D002736:Chloroplasts / Q000378:metabolism; D053487:DEAD-box RNA Helicases / Q000235:genetics* / Q000378:metabolism; D020043:Genes, Essential / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D018747:RNA, Chloroplast / Q000235:genetics / Q000378:metabolism; D012338:RNA, Ribosomal, 23S / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D018747:RNA, Chloroplast; D012338:RNA, Ribosomal, 23S; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins; C556415:RH39 protein, Arabidopsis; D053487:DEAD-box RNA Helicases; D012273:Ribulose-Bisphosphate Carboxylase