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Yokoyama T, Machida K, Iwasaki W, Shigeta T, Nishimoto M, Takahashi M, Sakamoto A, Yonemochi M, Harada Y, Shigematsu H, Shirouzu M, Tadakuma H, Imataka H, Ito T. HCV IRES Captures an Actively Translating 80S Ribosome. Mol Cell 2019; 74:1205-1214.e8. [PMID: 31080011 DOI: 10.1016/j.molcel.2019.04.022] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 02/20/2019] [Accepted: 04/15/2019] [Indexed: 01/06/2023]
Abstract
Translation initiation of hepatitis C virus (HCV) genomic RNA is induced by an internal ribosome entry site (IRES). Our cryoelectron microscopy (cryo-EM) analysis revealed that the HCV IRES binds to the solvent side of the 40S platform of the cap-dependently translating 80S ribosome. Furthermore, we obtained the cryo-EM structures of the HCV IRES capturing the 40S subunit of the IRES-dependently translating 80S ribosome. In the elucidated structures, the HCV IRES "body," consisting of domain III except for subdomain IIIb, binds to the 40S subunit, while the "long arm," consisting of domain II, remains flexible and does not impede the ongoing translation. Biochemical experiments revealed that the cap-dependently translating ribosome becomes a better substrate for the HCV IRES than the free ribosome. Therefore, the HCV IRES is likely to efficiently induce the translation initiation of its downstream mRNA with the captured translating ribosome as soon as the ongoing translation terminates.
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MESH Headings
- Binding Sites
- Cryoelectron Microscopy
- Eukaryotic Initiation Factors/chemistry
- Eukaryotic Initiation Factors/genetics
- Eukaryotic Initiation Factors/metabolism
- HEK293 Cells
- Hepacivirus/genetics
- Hepacivirus/metabolism
- Host-Pathogen Interactions
- Humans
- Internal Ribosome Entry Sites
- Models, Molecular
- Nucleic Acid Conformation
- Peptide Chain Initiation, Translational
- RNA, Viral/chemistry
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Ribosome Subunits, Large, Eukaryotic/genetics
- Ribosome Subunits, Large, Eukaryotic/metabolism
- Ribosome Subunits, Large, Eukaryotic/ultrastructure
- Ribosome Subunits, Small, Eukaryotic/genetics
- Ribosome Subunits, Small, Eukaryotic/metabolism
- Ribosome Subunits, Small, Eukaryotic/ultrastructure
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Affiliation(s)
- Takeshi Yokoyama
- RIKEN Center for Biosystems Dynamics Research, Tsurumi-ku, Yokohama 230-0045, Japan; Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Kodai Machida
- Graduate School of Engineering, University of Hyogo, Himeji, Hyogo 671-2280, Japan
| | - Wakana Iwasaki
- RIKEN Center for Biosystems Dynamics Research, Tsurumi-ku, Yokohama 230-0045, Japan; Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Tomoaki Shigeta
- Graduate School of Engineering, University of Hyogo, Himeji, Hyogo 671-2280, Japan
| | - Madoka Nishimoto
- RIKEN Center for Biosystems Dynamics Research, Tsurumi-ku, Yokohama 230-0045, Japan; Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Mari Takahashi
- RIKEN Center for Biosystems Dynamics Research, Tsurumi-ku, Yokohama 230-0045, Japan; Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Ayako Sakamoto
- RIKEN Center for Biosystems Dynamics Research, Tsurumi-ku, Yokohama 230-0045, Japan; Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Mayumi Yonemochi
- RIKEN Center for Biosystems Dynamics Research, Tsurumi-ku, Yokohama 230-0045, Japan; Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Yoshie Harada
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Hideki Shigematsu
- Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan; Life Science Research Infrastructure Group, RIKEN SPring-8 Center, Sayo-gun, Hyogo 679-5148, Japan
| | - Mikako Shirouzu
- RIKEN Center for Biosystems Dynamics Research, Tsurumi-ku, Yokohama 230-0045, Japan; Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Hisashi Tadakuma
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan.
| | - Hiroaki Imataka
- Graduate School of Engineering, University of Hyogo, Himeji, Hyogo 671-2280, Japan.
| | - Takuhiro Ito
- RIKEN Center for Biosystems Dynamics Research, Tsurumi-ku, Yokohama 230-0045, Japan; Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan.
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2
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Masutani M, Sonenberg N, Yokoyama S, Imataka H. Reconstitution reveals the functional core of mammalian eIF3. EMBO J 2007; 26:3373-83. [PMID: 17581632 PMCID: PMC1933396 DOI: 10.1038/sj.emboj.7601765] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2007] [Accepted: 05/24/2007] [Indexed: 11/08/2022] Open
Abstract
Eukaryotic translation initiation factor (eIF)3 is the largest eIF ( approximately 650 kDa), consisting of 10-13 different polypeptide subunits in mammalian cells. To understand the role of each subunit, we successfully reconstituted a human eIF3 complex consisting of 11 subunits that promoted the recruitment of the 40S ribosomal subunit to mRNA. Strikingly, the eIF3g and eIF3i subunits, which are evolutionarily conserved between human and the yeast Saccharomyces cerevisiae are dispensable for active mammalian eIF3 complex formation. Extensive deletion analyses suggest that three evolutionarily conserved subunits (eIF3a, eIF3b, and eIF3c) and three non-conserved subunits (eIF3e, eIF3f, and eIF3h) comprise the functional core of mammalian eIF3.
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Affiliation(s)
| | - Nahum Sonenberg
- Department of Biochemistry and McGill Cancer Center, McGill University, Montreal, Quebec, Canada
| | - Shigeyuki Yokoyama
- RIKEN Genomic Sciences Center, Tsurumi-ku, Yokohama, Japan
- Department of Biophysics and Biochemistry, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan
| | - Hiroaki Imataka
- RIKEN Genomic Sciences Center, Tsurumi-ku, Yokohama, Japan
- Protein Research Group, RIKEN Genomic Sciences Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan. Tel.: +81 45 503 9461; Fax: +81 45 503 9460; E-mail:
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3
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Kim JT, Kim KD, Song EY, Lee HG, Kim JW, Kim JW, Chae SK, Kim E, Lee MS, Yang Y, Lim JS. Apoptosis-inducing factor (AIF) inhibits protein synthesis by interacting with the eukaryotic translation initiation factor 3 subunit p44 (eIF3g). FEBS Lett 2006; 580:6375-83. [PMID: 17094969 DOI: 10.1016/j.febslet.2006.10.049] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2006] [Revised: 10/25/2006] [Accepted: 10/25/2006] [Indexed: 11/23/2022]
Abstract
Apoptosis-inducing factor (AIF) is a ubiquitous FAD-binding flavoprotein comprised of 613 amino acids and plays an important role in caspase-independent apoptosis. During apoptotic induction, AIF is translocated from the mitochondrial intermembrane space to the nucleus, where it interacts with DNA and activates a nuclear endonuclease. By performing a yeast two-hybrid screen with mature AIF, we have isolated the eukaryotic translation initiation factor 3 subunit p44 (eIF3g). Our deletion mutant analysis revealed that the eIF3g N-terminus interacts with the C-terminal region of AIF. The direct interaction between AIF and eIF3g was confirmed in a GST pull-down assay and also verified by the results of co-immunoprecipitation and confocal microscopy studies. Using an in vitro TNT coupled transcription-translation system, we found that mature AIF could inhibit newly-translated protein synthesis and this inhibition was significantly blocked by eIF3g competitively. These results were also confirmed in cells. In addition, mature AIF overexpression specifically resulted in the activation of caspase-7, thereby amplifying the inhibition of protein synthesis including eIF3g cleavage. Our data suggest that eIF3g is one of the cytosolic targets that interacts with mature AIF, and provide insight into the AIF's cellular functions of the inhibition of protein synthesis during apoptosis.
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Affiliation(s)
- Jong-Tae Kim
- Department of Biological Sciences, Research Center for Women's Diseases, Sookmyung Women's University, Chungpa-Dong, Yongsan-Gu, Seoul 140-742, Republic of Korea
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Lee SH, McCormick F. p97/DAP5 is a ribosome-associated factor that facilitates protein synthesis and cell proliferation by modulating the synthesis of cell cycle proteins. EMBO J 2006; 25:4008-19. [PMID: 16932749 PMCID: PMC1560370 DOI: 10.1038/sj.emboj.7601268] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2006] [Accepted: 07/12/2006] [Indexed: 11/09/2022] Open
Abstract
p97 (also referred to as DAP5, NAT1 or eIF4G2) has been proposed to act as a repressor of protein synthesis. However, we found that p97 is abundantly expressed in proliferating cells and p97 is recruited to ribosomes following growth factor stimulation. We also report that p97 binds eIF2beta through its C-terminal domain and localizes to ribosome through its N-terminal MIF4G domain. When overexpressed, p97 increases reporter luciferase activity. In contrast, overexpression of the C-terminal two-thirds of eukaryotic initiation factor 4GI (eIF4GI), a region that shares significant homology with p97, or the N-terminal MIF4G domain of p97 markedly inhibits reporter activity, the rate of global translation and cell proliferation. Conversely, downregulation of p97 levels by RNA interference also decreases the rate of global translation and inhibits cell proliferation. This coincides with an increase in p27/Kip1 protein levels and a marked decrease in CDK2 kinase activity. Taken together, our results demonstrate that p97 is functionally different from the closely related C-terminal two-thirds of eIF4GI and it can positively promote protein synthesis and cell proliferation.
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Affiliation(s)
- Sang Hyun Lee
- Cancer Research Institute and Comprehensive Cancer Center, University of California, San Francisco, CA, USA
| | - Frank McCormick
- Cancer Research Institute and Comprehensive Cancer Center, University of California, San Francisco, CA, USA
- Cancer Research Institute and Comprehensive Cancer Center, University of California, 2340 Sutter St N315, San Francisco, CA 94115, USA. Tel.: +1 415 502 1707; Fax: +1 415 502 1712; E-mail:
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Shahbazian D, Roux PP, Mieulet V, Cohen MS, Raught B, Taunton J, Hershey JWB, Blenis J, Pende M, Sonenberg N. The mTOR/PI3K and MAPK pathways converge on eIF4B to control its phosphorylation and activity. EMBO J 2006; 25:2781-91. [PMID: 16763566 PMCID: PMC1500846 DOI: 10.1038/sj.emboj.7601166] [Citation(s) in RCA: 381] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2005] [Accepted: 05/04/2006] [Indexed: 11/09/2022] Open
Abstract
The eukaryotic translation initiation factor 4B (eIF4B) plays a critical role in recruiting the 40S ribosomal subunit to the mRNA. In response to insulin, eIF4B is phosphorylated on Ser422 by S6K in a rapamycin-sensitive manner. Here we demonstrate that the p90 ribosomal protein S6 kinase (RSK) phosphorylates eIF4B on the same residue. The relative contribution of the RSK and S6K modules to the phosphorylation of eIF4B is growth factor-dependent, and the two phosphorylation events exhibit very different kinetics. The S6K and RSK proteins are members of the AGC protein kinase family, and require PDK1 phosphorylation for activation. Consistent with this requirement, phosphorylation of eIF4B Ser422 is abrogated in PDK1 null embryonic stem cells. Phosphorylation of eIF4B on Ser422 by RSK and S6K is physiologically significant, as it increases the interaction of eIF4B with the eukaryotic translation initiation factor 3.
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Affiliation(s)
- David Shahbazian
- Department of Biochemistry, McGill Cancer Centre, McGill University, Montreal, Quebec, Canada
| | - Philippe P Roux
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Virginie Mieulet
- INSERM, Avenir, U584, Université Paris 5, Faculté de Médecine Necker-Enfants Malades, Paris, France
| | - Michael S Cohen
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
| | - Brian Raught
- Ontario Cancer Institute and McLaughlin Centre for Molecular Medicine, MaRS Centre, Toronto, Ontario, Canada
| | - Jack Taunton
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
| | - John W B Hershey
- Department of Biological Chemistry, School of Medicine, University of California, Davis, CA, USA
| | - John Blenis
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Mario Pende
- INSERM, Avenir, U584, Université Paris 5, Faculté de Médecine Necker-Enfants Malades, Paris, France
| | - Nahum Sonenberg
- Department of Biochemistry, McGill Cancer Centre, McGill University, Montreal, Quebec, Canada
- Department of Biochemistry, McGill University, McIntyre Medical Sciences Building, 3655 Promenade Sir-William-Osler, Rm. 807, Montreal, Quebec, Canada H3G 1Y6. Tel.: +1 514 398 7274; Fax: +1 514 398 1287; E-mail:
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Imataka H, Olsen HS, Sonenberg N. A new translational regulator with homology to eukaryotic translation initiation factor 4G. EMBO J 1997; 16:817-25. [PMID: 9049310 PMCID: PMC1169682 DOI: 10.1093/emboj/16.4.817] [Citation(s) in RCA: 174] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Translation initiation in eukaryotes is facilitated by the cap structure, m7GpppN (where N is any nucleotide). Eukaryotic translation initiation factor 4F (eIF4F) is a cap binding protein complex that consists of three subunits: eIF4A, eIF4E and eIF4G. eIF4G interacts directly with eIF4E and eIF4A. The binding site of eIF4E resides in the N-terminal third of eIF4G, while eIF4A and eIF3 binding sites are present in the C-terminal two-thirds. Here, we describe a new eukaryotic translational regulator (hereafter called p97) which exhibits 28% identity to the C-terminal two-thirds of eIF4G. p97 mRNA has no initiator AUG and translation starts exclusively at a GUG codon. The GUG-initiated open reading frame (907 amino acids) has no canonical eIF4E binding site. p97 binds to eIF4A and eIF3, but not to eIF4E. Transient transfection experiments show that p97 suppresses both cap-dependent and independent translation, while eIF4G supports both translation pathways. Furthermore, inducible expression of p97 reduces overall protein synthesis. These results suggest that p97 functions as a general repressor of translation by forming translationally inactive complexes that include eIF4A and eIF3, but exclude eIF4E.
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Affiliation(s)
- H Imataka
- Department of Biochemistry and McGill Cancer Centre, McGill University, Montreal, Quebec, Canada
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Méthot N, Rom E, Olsen H, Sonenberg N. The human homologue of the yeast Prt1 protein is an integral part of the eukaryotic initiation factor 3 complex and interacts with p170. J Biol Chem 1997; 272:1110-6. [PMID: 8995410 DOI: 10.1074/jbc.272.2.1110] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Eukaryotic initiation factor 3 (eIF3) is a large multisubunit complex that stabilizes the ternary complex, eIF2 x GTP x tRNA(Met)i and promotes mRNA binding to the 40 S ribosomal subunit. eIF3 also functions as a ribosome subunit anti-association factor. The molecular mechanisms by which eIF3 exerts these functions are poorly understood. We describe here the cloning of the cDNA encoding the human homologue of the yeast eIF3 subunit Prt1. The human PRT1 cDNA encodes a protein of predicted molecular mass of 98.9 kDa that migrates at 116 kDa on SDS-polyacrylamide gels. Human and yeast Prt1 share 31% identity and 50% similarity at the amino acid level. The homology is distributed throughout the entire protein, except for the amino terminus, and is particularly high in the central portion of the protein, which contains a putative RNA recognition motif. hPrt1 is recognized by an antibody raised against eIF3, and an affinity-purified antibody to recombinant hPrt1 recognizes a protein migrating at 116 kDa in a purified eIF3 preparation. Far Western analysis shows that hPrt1 interacts directly with the p170 subunit of eIF3. Mapping studies identify the RNA recognition motif as the region required for association with p170. Taken together, these experiments demonstrate that hPrt1 is a component of eIF3. Our data, combined with those of Hershey and co-workers, suggest that mammalian eIF3 is composed of at least 10 subunits: p170, p116 (hPrt1), p110, p66, p48, p47, p44, p40, p36, and p35.
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Affiliation(s)
- N Méthot
- Department of Biochemistry, McGill University, Montréal, Québec, Canada
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Méthot N, Song MS, Sonenberg N. A region rich in aspartic acid, arginine, tyrosine, and glycine (DRYG) mediates eukaryotic initiation factor 4B (eIF4B) self-association and interaction with eIF3. Mol Cell Biol 1996; 16:5328-34. [PMID: 8816444 PMCID: PMC231531 DOI: 10.1128/mcb.16.10.5328] [Citation(s) in RCA: 147] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The binding of mRNA to the ribosome is mediated by eukaryotic initiation factors eukaryotic initiation factor 4F (eIF4F), eIF4B, eIF4A, and eIF3, eIF4F binds to the mRNA cap structure and, in combination with eIF4B, is believed to unwind the secondary structure in the 5' untranslated region to facilitate ribosome binding. eIF3 associates with the 40S ribosomal subunit prior to mRNA binding. eIF4B copurifies with eIF3 and eIF4F through several purification steps, suggesting the involvement of a multisubunit complex during translation initiation. To understand the mechanism by which eIF4B promotes 40S ribosome binding to the mRNA, we studied its interactions with partner proteins by using a filter overlay (protein-protein [far Western]) assay and the two-hybrid system. In this report, we show that eIF4B self-associates and also interacts directly with the p170 subunit of eIF3. A region rich in aspartic acid, arginine, tyrosine, and glycine, termed the DRYG domain, is sufficient for self-association of eIF4B, both in vitro and in vivo, and for interaction with the p170 subunit of eIF3. These experiments suggest that eIF4B participates in mRNA-ribosome binding by acting as an intermediary between the mRNA and eIF3, via a direct interaction with the p170 subunit of eIF3.
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Affiliation(s)
- N Méthot
- Department of Biochemistry, McGill University, Montréal, Québec, Canada
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Schneider HR, Reichert GH, Issinger OG. Enhanced casein kinase II activity during mouse embryogenesis. Identification of a 110-kDa phosphoprotein as the major phosphorylation product in mouse embryos and Krebs II mouse ascites tumor cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 1986; 161:733-8. [PMID: 3466791 DOI: 10.1111/j.1432-1033.1986.tb10501.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Mouse embryos at various stages of development were used to study the relationship of protein kinase activities with normal embryogenesis. Casein kinase II (CKII) activity in developing mouse embryos shows a 3-4-fold activity increase at day 12 of gestation. Together with the CKII activity, increased phosphorylation of a 110-kDa protein is observed. Treatment of the embryo extracts with heparin, a highly specific inhibitor of CKII activity, results in a drastic reduction of the 110-kDa protein phosphorylation indicating that the protein might be a CKII-specific substrate. Rapidly proliferating mouse tumour cells also show an enhanced CKII activity. Here too, a 110-kDa phosphoprotein was the major phosphoryl acceptor. Partial proteolytic digestion shows that both proteins are identical. Other protein kinases tested (cAMP- and cGMP-dependent protein kinases) only show a basal level of enzyme activity with minor alterations throughout the different stages of embryogenesis investigated.
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Clemens MJ, Tilleray VJ. Inhibition of polypeptide chain initiation in Daudi cells by interferons. Evidence that activity of initiation factor eIF-2 and availability of mRNA are unimpaired. Biochem J 1986; 237:877-84. [PMID: 2432877 PMCID: PMC1147070 DOI: 10.1042/bj2370877] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The accompanying paper [McNurlan & Clemens (1986) Biochem. J. 237, 871-876] shows that the inhibition of proliferation of Daudi cells by human interferons is associated with impairment of the overall rate of protein synthesis. We have examined whether two of the mechanisms which are believed to control translation in interferon-treated virus-infected cells may be responsible for the inhibition of protein synthesis during the antiproliferative response in these uninfected cells. Although the rate of polypeptide chain initiation is lower in interferon-treated Daudi cells, as indicated by the disaggregation of polysomes, there is no significant inhibition of activity of initiation factor eIF-2 or of [40 S . Met-tRNAf] initiation complex formation in cell extracts. The phosphorylation state of the alpha subunit of eIF-2 remains unaltered. There is no major decrease in mRNA content as a proportion of total RNA up to 4 days of interferon treatment, as judged by poly(A) content, although the amount of total mRNA/10(6) cells eventually declines. The mRNA present in extracts from interferon-treated cells remains translatable when added to an mRNA-dependent reticulocyte lysate system. We conclude that neither the interferon-inducible eIF-2 protein kinase pathway nor the 2',5'-oligo(adenylate)-ribonuclease L pathway are responsible for the inhibition of polypeptide chain initiation. Rather, the data suggest impairment at the level of formation of [80 S ribosome X mRNA] initiation complexes.
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