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Saegusa C, Kakegawa W, Miura E, Aimi T, Mogi S, Harada T, Yamashita T, Yuzaki M, Fujioka M. Brain-Specific Angiogenesis Inhibitor 3 Is Expressed in the Cochlea and Is Necessary for Hearing Function in Mice. Int J Mol Sci 2023; 24:17092. [PMID: 38069416 PMCID: PMC10707444 DOI: 10.3390/ijms242317092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 11/27/2023] [Accepted: 11/29/2023] [Indexed: 12/18/2023] Open
Abstract
Mammalian auditory hair cells transduce sound-evoked traveling waves in the cochlea into nerve stimuli, which are essential for hearing function. Pillar cells located between the inner and outer hair cells are involved in the formation of the tunnel of Corti, which incorporates outer-hair-cell-driven fluid oscillation and basilar membrane movement, leading to the fine-tuned frequency-specific perception of sounds by the inner hair cells. However, the detailed molecular mechanism underlying the development and maintenance of pillar cells remains to be elucidated. In this study, we examined the expression and function of brain-specific angiogenesis inhibitor 3 (Bai3), an adhesion G-protein-coupled receptor, in the cochlea. We found that Bai3 was expressed in hair cells in neonatal mice and pillar cells in adult mice, and, interestingly, Bai3 knockout mice revealed the abnormal formation of pillar cells, with the elevation of the hearing threshold in a frequency-dependent manner. Furthermore, old Bai3 knockout mice showed the degeneration of hair cells and spiral ganglion neurons in the basal turn. The results suggest that Bai3 plays a crucial role in the development and/or maintenance of pillar cells, which, in turn, are necessary for normal hearing function. Our results may contribute to understanding the mechanisms of hearing loss in human patients.
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Affiliation(s)
- Chika Saegusa
- Department of Molecular Genetics, Kitasato University School of Medicine, Kanagawa 252-0374, Japan;
- Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Wataru Kakegawa
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan; (W.K.); (E.M.); (T.A.); (M.Y.)
| | - Eriko Miura
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan; (W.K.); (E.M.); (T.A.); (M.Y.)
| | - Takahiro Aimi
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan; (W.K.); (E.M.); (T.A.); (M.Y.)
| | - Sachiyo Mogi
- Department of Otorhinolaryngology, Head and Neck Surgery, Kitasato University, Kanagawa 252-0374, Japan; (S.M.); (T.Y.)
| | - Tatsuhiko Harada
- Department of Otolaryngology, International University of Health and Welfare, Shizuoka 413-0012, Japan;
| | - Taku Yamashita
- Department of Otorhinolaryngology, Head and Neck Surgery, Kitasato University, Kanagawa 252-0374, Japan; (S.M.); (T.Y.)
| | - Michisuke Yuzaki
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan; (W.K.); (E.M.); (T.A.); (M.Y.)
| | - Masato Fujioka
- Department of Molecular Genetics, Kitasato University School of Medicine, Kanagawa 252-0374, Japan;
- Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, Tokyo 160-8582, Japan
- Clinical and Translational Research Center, Keio University Hospital, Tokyo 162-8582, Japan
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Aimi T, Matsuda K, Yuzaki M. C1ql1-Bai3 signaling is necessary for climbing fiber synapse formation in mature Purkinje cells in coordination with neuronal activity. Mol Brain 2023; 16:61. [PMID: 37488606 PMCID: PMC10367388 DOI: 10.1186/s13041-023-01048-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 07/05/2023] [Indexed: 07/26/2023] Open
Abstract
Changes in neural activity induced by learning and novel environments have been reported to lead to the formation of new synapses in the adult brain. However, the underlying molecular mechanism is not well understood. Here, we show that Purkinje cells (PCs), which have established adult-type monosynaptic innervation by climbing fibers (CFs) after elimination of weak CFs during development, can be reinnervated by multiple CFs by increased expression of the synaptic organizer C1ql1 in CFs or Bai3, a receptor for C1ql1, in PCs. In the adult cerebellum, CFs are known to have transverse branches that run in a mediolateral direction without forming synapses with PCs. Electrophysiological, Ca2+-imaging and immunohistochemical studies showed that overexpression of C1ql1 or Bai3 caused these CF transverse branches to elongate and synapse on the distal dendrites of mature PCs. Mature PCs were also reinnervated by multiple CFs when the glutamate receptor GluD2, which is essential for the maintenance of synapses between granule cells and PCs, was deleted. Interestingly, the effect of GluD2 knockout was not observed in Bai3 knockout PCs. In addition, C1ql1 levels were significantly upregulated in CFs of GluD2 knockout mice, suggesting that endogenous, not overexpressed, C1ql1-Bai3 signaling could regulate the reinnervation of mature PCs by CFs. Furthermore, the effects of C1ql1 and Bai3 overexpression required neuronal activity in the PC and CF, respectively. C1ql1 immunoreactivity at CF-PC synapses was reduced when the neuronal activity of CFs was suppressed. These results suggest that C1ql1-Bai3 signaling may mediate CF synaptogenesis in mature PCs, potentially in concert with neuronal activity.
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Affiliation(s)
- Takahiro Aimi
- Department of Physiology, Keio University School of Medicine, Tokyo, 160-8582, Japan
| | - Keiko Matsuda
- Department of Physiology, Keio University School of Medicine, Tokyo, 160-8582, Japan
| | - Michisuke Yuzaki
- Department of Physiology, Keio University School of Medicine, Tokyo, 160-8582, Japan.
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3
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Aimi T, Meguro T, Kobayashi A, Hosoya T, Yoshida S. Nucleophilic transformations of azido-containing carbonyl compounds via protection of the azido group. Chem Commun (Camb) 2021; 57:6062-6065. [PMID: 34036976 DOI: 10.1039/d1cc01143j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Nucleophilic transformations of azido-containing carbonyl compounds are discussed. The phosphazide formation from azides and di(tert-butyl)(4-(dimethylamino)phenyl)phosphine (Amphos) enabled transformations of carbonyl groups with nucleophiles such as lithium aluminum hydride and organometallic reagents. The good stability of the phosphazide moiety allowed us to perform consecutive transformations of a diazide through triazole formation and the Grignard reaction.
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Affiliation(s)
- Takahiro Aimi
- Laboratory of Chemical Bioscience, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (TMDU), 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-0062, Japan.
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4
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Hamoud N, Tran V, Aimi T, Kakegawa W, Lahaie S, Thibault MP, Pelletier A, Wong GW, Kim IS, Kania A, Yuzaki M, Bouvier M, Côté JF. Spatiotemporal regulation of the GPCR activity of BAI3 by C1qL4 and Stabilin-2 controls myoblast fusion. Nat Commun 2018; 9:4470. [PMID: 30367035 PMCID: PMC6203814 DOI: 10.1038/s41467-018-06897-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Accepted: 10/05/2018] [Indexed: 11/09/2022] Open
Abstract
Myoblast fusion is tightly regulated during development and regeneration of muscle fibers. BAI3 is a receptor that orchestrates myoblast fusion via Elmo/Dock1 signaling, but the mechanisms regulating its activity remain elusive. Here we report that mice lacking BAI3 display small muscle fibers and inefficient muscle regeneration after cardiotoxin-induced injury. We describe two proteins that repress or activate BAI3 in muscle progenitors. We find that the secreted C1q-like1-4 proteins repress fusion by specifically interacting with BAI3. Using a proteomic approach, we identify Stabilin-2 as a protein that interacts with BAI3 and stimulates its fusion promoting activity. We demonstrate that Stabilin-2 activates the GPCR activity of BAI3. The resulting activated heterotrimeric G-proteins contribute to the initial recruitment of Elmo proteins to the membrane, which are then stabilized on BAI3 through a direct interaction. Collectively, our results demonstrate that the activity of BAI3 is spatiotemporally regulated by C1qL4 and Stabilin-2 during myoblast fusion.
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Affiliation(s)
- Noumeira Hamoud
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC, H2W 1R7, Canada.,Département de Médecine (Programmes de Biologie Moléculaire), Université de Montréal, Montréal, QC, H3T 1J4, Canada
| | - Viviane Tran
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC, H2W 1R7, Canada.,Département de Biochimie, Université de Montréal, Montréal, QC, H3T 1J4, Canada
| | - Takahiro Aimi
- Department of Physiology, Keio University School of Medicine, Tokyo, 160-8582, Japan.,Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JT), Tokyo, 102-0075, Japan
| | - Wataru Kakegawa
- Department of Physiology, Keio University School of Medicine, Tokyo, 160-8582, Japan.,Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JT), Tokyo, 102-0075, Japan
| | - Sylvie Lahaie
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC, H2W 1R7, Canada.,Integrated Program in Neuroscience, McGill University, Montréal, QC, H3A 2B4, Canada
| | - Marie-Pier Thibault
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC, H2W 1R7, Canada
| | - Ariane Pelletier
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC, H2W 1R7, Canada
| | - G William Wong
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.,Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - In-San Kim
- Biomedical Research Institute, Korea Institute Science and Technology, Seoul, 136-791, Republic of Korea.,KU-KIST school, Korea University, Seoul, 136-701, Republic of Korea
| | - Artur Kania
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC, H2W 1R7, Canada.,Integrated Program in Neuroscience, McGill University, Montréal, QC, H3A 2B4, Canada.,Department of Anatomy and Cell Biology, McGill University, Montréal, QC, H3A 1A3, Canada
| | - Michisuke Yuzaki
- Department of Physiology, Keio University School of Medicine, Tokyo, 160-8582, Japan.,Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JT), Tokyo, 102-0075, Japan
| | - Michel Bouvier
- Département de Biochimie, Université de Montréal, Montréal, QC, H3T 1J4, Canada.,Institut de Recherches en Immunologie et Cancérologie (IRIC), Université de Montréal, Montréal, QC, Canada, H3C 3J7
| | - Jean-François Côté
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC, H2W 1R7, Canada. .,Département de Médecine (Programmes de Biologie Moléculaire), Université de Montréal, Montréal, QC, H3T 1J4, Canada. .,Département de Biochimie, Université de Montréal, Montréal, QC, H3T 1J4, Canada. .,Department of Anatomy and Cell Biology, McGill University, Montréal, QC, H3A 1A3, Canada.
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Suzuki K, Aimi T, Ishihara T, Mizushima T. Identification of approved drugs that inhibit the binding of amyloid β oligomers to ephrin type-B receptor 2. FEBS Open Bio 2016; 6:461-8. [PMID: 27419051 PMCID: PMC4856424 DOI: 10.1002/2211-5463.12056] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 02/26/2016] [Accepted: 03/10/2016] [Indexed: 12/29/2022] Open
Abstract
Ephrin type‐B receptor 2 (EphB2) is a member of the receptor tyrosine kinase family and plays an important role in learning and memory functions. In patients with Alzheimer's disease (AD) and in mouse models of AD, a reduction in the hippocampal EphB2 level is observed. It was recently reported that normalization of the EphB2 level in the dentate gyrus rescues memory function in a mouse model of AD, suggesting that drugs that restore EphB2 levels may be beneficial in the treatment of AD. Amyloid β (Aβ) oligomers, which are believed to be key molecules involved in the pathogenesis of AD, induce EphB2 degradation through their direct binding to EphB2. Thus, compounds that inhibit the binding of Aβ oligomers to EphB2 may be beneficial. Here, we screened for such compounds from drugs already approved for clinical use in humans. Utilizing a cell‐free screening assay, we determined that dihydroergotamine mesilate, bromocriptine mesilate, cepharanthine, and levonorgestrel inhibited the binding of Aβ oligomers to EphB2 but not to cellular prion protein, another endogenous receptor for Aβ oligomers. Additionally, these four compounds did not affect the binding between EphB2 and ephrinB2, an endogenous ligand for EphB2, suggesting that the compounds selectively inhibited the binding of Aβ oligomers to EphB2. This is the first identification of compounds that selectively inhibit the binding of Aβ oligomers to EphB2. These results suggest that these four compounds may be safe and effective drugs for treatment of AD.
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Affiliation(s)
- Koichiro Suzuki
- Division of Drug Discovery and Development Faculty of Pharmacy Keio University Minato-ku Tokyo Japan; Research Fellow of Japan Society for the Promotion of Science Chiyoda-ku Tokyo Japan
| | - Takahiro Aimi
- Division of Drug Discovery and Development Faculty of Pharmacy Keio University Minato-ku Tokyo Japan
| | - Tomoaki Ishihara
- Division of Drug Discovery and Development Faculty of Pharmacy Keio University Minato-ku Tokyo Japan
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Aimi T, Suzuki K, Hoshino T, Mizushima T. Dextran sulfate sodium inhibits amyloid-β oligomer binding to cellular prion protein. J Neurochem 2015; 134:611-7. [PMID: 25963375 DOI: 10.1111/jnc.13166] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 04/16/2015] [Accepted: 04/30/2015] [Indexed: 11/30/2022]
Abstract
Amyloid-β peptide (Aβ), especially its oligomeric form, is believed to play an important role in the pathogenesis of Alzheimer's disease (AD). To this end, the binding of Aβ oligomer to cellular prion protein (PrP(C)) plays an important role in synaptic dysfunction in a mouse model of AD. Here, we have screened for compounds that inhibit Aβ oligomer binding to PrP(C) from medicines already used clinically (Mizushima Approved Medicine Library 1), and identified dextran sulfate sodium (DSS) as a candidate. In a cell-free assay, DSS inhibited Aβ oligomer binding to PrP(C) but not to ephrin receptor B2, another endogenous receptor for Aβ oligomers, suggesting that the drug's action is specific to the binding of Aβ oligomer to PrP(C) . Dextran on the other hand did not affect this binding. DSS also suppressed Aβ oligomer binding to cells expressing PrP(C) but not to control cells. Furthermore, while incubation of mouse hippocampal slices with Aβ oligomers inhibited the induction of long-term potentiation, simultaneous treatment with DSS restored the long-term potentiation. As DSS has already been approved for use in patients with hypertriglyceridemia, and its safety in humans has been confirmed, we propose further analysis of this drug as a candidate for AD treatment. Amyloid-β peptide (Aβ) oligomer-binding to cellular prion protein (PrP(C) ) is important in synaptic dysfunction in Alzheimer's disease (AD). We found here that dextran sulfate sodium (DSS) inhibits Aβ oligomer binding to PrP(C) . Simultaneous treatment of hippocampal slices with DSS restored long-term potentiation (LTP) in the presence of Aβ oligomers. Since DSS has already been approved for clinical use, we propose this drug is a candidate drug for AD treatment.
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Palapala VA, Aimi T, Inatomi S, Morinaga T. ITS-PCR-RFLP Method for Distinguishing Commercial Cultivars of Edible Mushroom, Flammulina velutipes. J Food Sci 2002. [DOI: 10.1111/j.1365-2621.2002.tb08763.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Maeshima H, Okuno E, Aimi T, Morinaga T, Itoh T. An archaeal protein homologous to mammalian SRP54 and bacterial Ffh recognizes a highly conserved region of SRP RNA. FEBS Lett 2001; 507:336-40. [PMID: 11696367 DOI: 10.1016/s0014-5793(01)02996-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The gene encoding the 54 kDa protein of signal recognition particle (SRP54) in the hyperthermophilic archaeon Pyrococcus furiosus has been cloned and sequenced. Recombinant P. furiosus SRP54 (pf-SRP54) and the N-terminal G-domain and C-terminal M-domain (pf-SRP54M) of pf-SRP54 with an amino-terminal addition of six histidine residues were expressed in Escherichia coli and subjected to binding experiments for SRP RNA, non-conserved 213-nucleotide RNA (helices 1, 2, 3, 4 and 5) and conserved 107-nucleotide RNA (helices 6 and 8) from SRP RNA. The RNA binding properties of the purified protein were determined by filter binding assays. The histidine-tagged pf-SRP54M bound specifically to the conserved 107-nucleotide RNA in the absence of pf-SRP19, unlike the eukaryotic homologue, with an apparent binding constant (K) of 18 nM.
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Affiliation(s)
- H Maeshima
- School of Bioresources, Hiroshima Prefectural University, Shobara City, 727-0023, Hiroshima, Japan
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Aimi T, Kano S, Wang Q, Morinaga T. Molecular cloning of three genes encoding G protein alpha subunits in the white root rot fungus, Rosellinia necatrix. Biosci Biotechnol Biochem 2001; 65:678-82. [PMID: 11330689 DOI: 10.1271/bbb.65.678] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Three genes encoding G protein alpha subunits were cloned from the white root rot fungus, Rosellinia necatrix, and characterized. Only one copy of each gene was present in the genome. The protein sequences of Rga1, Rga2, and Rga3 are very similar to those of MagA, MagB and MagC of Magnaporthe grisea, respectively. Moreover, Rga1 is similar to Mod-D which is closely related to vegetative incompatibility in Podospora anserina, which suggests that Rga1 is important in the vegetative incompatibility reaction in R. necatrix. Reverse transcription PCR (RT-PCR) analysis of Rga1, Rga2, and Rga3 mRNA expression showed that the three genes were all transcribed in R. necatrix cells.
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Affiliation(s)
- T Aimi
- Department of Bioresource Development, Hiroshima Prefectural University, Shobara-shi, Japan
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Abstract
A Northwestern analysis of Escherichia coli total proteins with radiolabeled 5S rRNA identified two novel 5S rRNA interacting proteins, a 70 kDa and a 37 kDa protein, and three ribosomal proteins reported on already. The N-terminal sequencing of the 70 kDa protein separated by SDS-PAGE from the high-salt-washed fraction of crude ribosome led to the discovery of a polypeptide identical in its first 10 amino acid residues to E. coli heat shock protein 70. The N-terminal eight amino acid sequence of the 37 kDa protein extracted from the high-salt-washed ribosome is identical to that of the ribosomal protein L2. In addition, the interaction of these proteins with 5S rRNA has been confirmed with gel mobility shift assays.
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Affiliation(s)
- S Okada
- School of Bioresources, Hiroshima Prefectural University, Shobara City, Hiroshima 727-0023, Japan
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Aimi T, Tsugawa K, Yano T, Morinaga T. Nucleotide sequences of genes for ribosomal protein L41 and tRNAThr(AGU) from Coprinus cinereus. Biochim Biophys Acta 1999; 1432:137-41. [PMID: 10366736 DOI: 10.1016/s0167-4838(99)00092-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The nucleotide sequences of genes for the homolog in Coprinus cinereus of the eukaryotic ribosomal protein L41 and for tRNAThr(AGU) are reported. The gene for tRNAThr(AGU) was located upstream of the gene for the L41 ribosomal protein, and these genes were adjacent to each other but in opposite orientations. The deduced amino acid sequence of ribosomal protein L41 exhibited strong homology to those of L41 proteins of several yeasts. The 56th amino acid of the deduced protein was proline, as it is in the L41 protein of a cycloheximide-sensitive strain of yeast. The putative secondary structure of the tRNA gene resembled the characteristic cloverleaf structure of tRNAs. Elements resembling an A-box and a B-box were found in the gene for tRNAThr(AGU). These boxes are known as internal promoter elements in genes for eukaryotic tRNAs.
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Affiliation(s)
- T Aimi
- Department of Information Machines and Interfaces, Faculty of Information Sciences, Hiroshima City University, 3-4-1 Ozuka-higashi, Asaminami-ku, Hiroshima 731-3194, Japan
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Aimi T, Yamada T, Yamashita M, Murooka Y. Characterization of the nuclear large-subunit rRNA-encoding gene and the group-I self-splicing intron from Chlorella ellipsoidea C-87. Gene 1994; 145:139-44. [PMID: 8045414 DOI: 10.1016/0378-1119(94)90337-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We found two group-I self-splicing introns in both the large subunit (LSU) and small subunit (SSU) of the nuclear rRNA-encoding genes (rDNA) of the unicellular green alga, Chlorella ellipsoidea C-87 (Ce). The primary and secondary structures of the LSU rRNA (3350 nt) and its intron (445 nt) were characterized. The intron was inserted in the conserved stem 32 of the LSU rRNA and contained all P1-P10 motifs of the group-IB intron. In vitro transcripts of the LSU rDNA containing the intron sequence displayed a strong self-splicing activity at high salt concentrations. The overall structure and splicing conditions of the LSU rRNA intron were, however, considerably different from those of the SSU rRNA intron of the same organism. These results suggest different origins and/or different evolutionary courses of these Ce introns.
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Affiliation(s)
- T Aimi
- Department of Fermentation Technology, Faculty of Engineering, Hiroshima University, Japan
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Abstract
We report the occurrence of self-splicing group I introns in viruses that infect the eukaryotic green alga Chlorella. The introns contained all the conserved features of primary sequence and secondary structure previously described for the group IB introns. The Chlorella viral introns (approximately 400 nt) self-spliced in vitro, yielding the typical group I intron splicing intermediates and products. Contrasting to eukaryotic nuclear group I introns, all of which are located in the rRNA genes, these introns were inserted in genes encoding proteins. In one case, the exons encoded a protein showing significant homology to the eukaryotic transcription factor SII (TFIIS), which may be important for viral gene expression. In another case, the gene for the open reading frame (ORF) of a 14.2 kDa polypeptide with unknown functions contained the intron. Scattered distribution of these introns among the viral species and their structural similarity to the group I introns of algae and protists indicated horizontal intron transmission. These eukaryotic viral introns offer an opportunity to understand how group I introns reach organisms of different phylogenetic kingdoms.
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Affiliation(s)
- T Yamada
- Department of Fermentation Technology, Faculty of Engineering, Hiroshima University, Japan
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14
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Abstract
We report the presence of a 442-bp group-I self-splicing intron in the nuclear small subunit (SSU) rRNA-encoding gene (rDNA) of the unicellular green alga, Chlorella ellipsoidea C-87 (C. saccharophila 211-1a). The intron was found to be inserted at a position within the highly conserved helix 48 that was close to the 3' terminus of the SSU rRNA. The position was exactly the same as previously identified for the Pneumocystis carinii intron. A secondary structure model for the C. ellipsoidea intron contained all P1-P10 motifs of the group-I introns. Although the overall secondary structure of the C. ellipsoidea intron was substantially different from that of the intron in the nuclear large subunit rDNA of Tetrahymena thermophila, the nucleotide (nt) sequences constituting the catalytic core were strikingly conserved between the two; only three of 48 nt were different. The C. ellipsoidea intron was autocatalytically excised from the transcript in vitro via the group-I mechanism under somewhat unique conditions. No SSU rDNA intron was found in six other Chlorella species, including C. fusca var. vacuolata, C. kessleri, C. minutissima, C. protothecoides, C. sorokiniana and C. vulgaris.
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Affiliation(s)
- T Aimi
- Department of Fermentation Technology, Faculty of Engineering, Hiroshima University, Japan
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Aimi T, Yamada T, Murooka Y. Group I self-splicing introns in both large and small subunit rRNA genes of Chlorella. Nucleic Acids Symp Ser 1993:159-160. [PMID: 8247750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We report the presence of Group I self-splicing introns in both nuclear small subunit (SSU) and large subunit (LSU) rRNAs of the unicellular green alga Chlorella ellipsoidea. The SSU intron (442 nt) was located at a position within the highly conserved helix 48 that was close to the 3' terminus of SSU rRNA: the position was exactly the same as previously reported for the Pneumocystis carinii Group I intron. The LSU intron (445 nt) was found in a highly conserved helix region (between positions 924-925) of LSU rRNA. Both introns can be folded into the secondary structures characteristic of Group I introns. The Chlorella introns self-spliced in vitro, yielding the typical Group-I intron splicing intermediates and products. Unlike the ordinary introns, however, splicing of the SSU intron was inhibited by high concentrations of monovalent cations at the second stage of splicing reaction. The Chlorella introns offer an opportunity to study the origin and evolution, physiological roles, and relationship between structure and splicing activity of Group I self-splicing introns.
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Affiliation(s)
- T Aimi
- Department of Fermentation Technology, Faculty of Engineering, Hiroshima University, Japan
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Aimi T, Yamada T, Murooka Y. Nucleotide sequence and secondary structure of 5.8S rRNA from the unicellular green alga, Chlorella ellipsoidea. Nucleic Acids Res 1992; 20:6098. [PMID: 1461741 PMCID: PMC334479 DOI: 10.1093/nar/20.22.6098] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Affiliation(s)
- T Aimi
- Department of Fermentation Technology, Faculty of Engineering, Hiroshima University, Japan
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