title: The eIF3 complex ofTrypanosoma brucei: composition conservation does not imply the conservation of structural assembly and subunits function.
abstract: The multisubunit eukaryotic initiation factor 3 (eIF3) plays multiple roles in translation but is poorly understood in trypanosomes. The putative subunits eIF3a and eIF3f ofTrypanosoma brucei(TbIF3a andTbIF3f) were overexpressed and purified, and 11 subunits were identified,TbIF3a through l minus j, which form a tight complex. BothTbIF3a andTbIF3f are essential for the viability ofT. bruceiRNAi knockdown of either of them severely reduced total translation and the ratio of the polysome/80S peak area.TbIF3f andTbIF3a RNAi cell lines were modified to express tagged-TbIF3a and -TbIF3f, respectively. RNAi in combination with affinity purification assays indicated that both subunits are variably required forTbIF3 stability and integrity. The relative abundance of other subunits in theTbIF3f-tag complex changed little uponTbIF3a depletion; while only subunitsTbIF3b, i, and e copurified comparably withTbIF3a-tag uponTbIF3f depletion. A genome-wide UV-crosslinking assay showed that severalTbIF3 subunits have direct RNA-binding activity, withTbIF3c showing the strongest signal. In addition, CrPV IRES, but neither EMCV IRES nor HCV IRES, was found to mediate translation inT. bruceiThese results together imply that the structure ofTbIF3 and the subunits function have trypanosome-specific features, although the composition is evolutionarily conserved.
authors.affiliation: Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China.|Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China.
authors.forename: Kunrao
authors.initials: K
authors.lastname: Li
authors.affiliation: Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China.|Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China.
authors.forename: Shuru
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Chengde Nursing Vocational College, Chengde 067000, China.
authors.forename: Qixuan
authors.initials: Q
authors.lastname: Guo
authors.affiliation: Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China.|Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
authors.affiliation: Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China.|Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China.
authors.forename: De-Hua
authors.initials: DH
authors.lastname: Lai
authors.affiliation: Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China.|Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China.
authors.forename: Zhao-Rong
authors.initials: ZR
authors.lastname: Lun
authors.affiliation: Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China xmguo2005@yahoo.com lsslzr@mail.sysu.edu.cn.|Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China.
authors.forename: Xuemin
authors.initials: X
authors.lastname: Guo
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D056629:Dicistroviridae / Q000235:genetics; D004686:Encephalomyocarditis virus / Q000235:genetics; D039621:Eukaryotic Initiation Factor-3 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D016174:Hepacivirus / Q000235:genetics; D000067556:Internal Ribosome Entry Sites; D011485:Protein Binding; D014176:Protein Biosynthesis; D055550:Protein Stability; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016053:RNA, Protozoan / Q000235:genetics* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D039621:Eukaryotic Initiation Factor-3; D000067556:Internal Ribosome Entry Sites; D021122:Protein Subunits; D015800:Protozoan Proteins; D016053:RNA, Protozoan; D034741:RNA, Small Interfering
keywords: eukaryotic initiation factor 3; translation; trypanosome