ジャーナル: Nature / 年: 2013 タイトル: Hepatitis-C-virus-like internal ribosome entry sites displace eIF3 to gain access to the 40S subunit. 著者: Yaser Hashem / Amedee des Georges / Vidya Dhote / Robert Langlois / Hstau Y Liao / Robert A Grassucci / Tatyana V Pestova / Christopher U T Hellen / Joachim Frank / 要旨: Hepatitis C virus (HCV) and classical swine fever virus (CSFV) messenger RNAs contain related (HCV-like) internal ribosome entry sites (IRESs) that promote 5'-end independent initiation of ...Hepatitis C virus (HCV) and classical swine fever virus (CSFV) messenger RNAs contain related (HCV-like) internal ribosome entry sites (IRESs) that promote 5'-end independent initiation of translation, requiring only a subset of the eukaryotic initiation factors (eIFs) needed for canonical initiation on cellular mRNAs. Initiation on HCV-like IRESs relies on their specific interaction with the 40S subunit, which places the initiation codon into the P site, where it directly base-pairs with eIF2-bound initiator methionyl transfer RNA to form a 48S initiation complex. However, all HCV-like IRESs also specifically interact with eIF3 (refs 2, 5-7, 9-12), but the role of this interaction in IRES-mediated initiation has remained unknown. During canonical initiation, eIF3 binds to the 40S subunit as a component of the 43S pre-initiation complex, and comparison of the ribosomal positions of eIF3 and the HCV IRES revealed that they overlap, so that their rearrangement would be required for formation of ribosomal complexes containing both components. Here we present a cryo-electron microscopy reconstruction of a 40S ribosomal complex containing eIF3 and the CSFV IRES. Remarkably, although the position and interactions of the CSFV IRES with the 40S subunit in this complex are similar to those of the HCV IRES in the 40S-IRES binary complex, eIF3 is completely displaced from its ribosomal position in the 43S complex, and instead interacts through its ribosome-binding surface exclusively with the apical region of domain III of the IRES. Our results suggest a role for the specific interaction of HCV-like IRESs with eIF3 in preventing ribosomal association of eIF3, which could serve two purposes: relieving the competition between the IRES and eIF3 for a common binding site on the 40S subunit, and reducing formation of 43S complexes, thereby favouring translation of viral mRNAs.
ダウンロード / ファイル: emd_2450.map.gz / 形式: CCP4 / 大きさ: 39.7 MB / タイプ: IMAGE STORED AS FLOATING POINT NUMBER (4 BYTES)
注釈
Reconstruction of a mutant Classical Swine Fever Virus IRES bound to the Rabbit 40S subunit and DHX29.
ボクセルのサイズ
X=Y=Z: 2.245 Å
密度
表面レベル
登録者による: 0.07 / ムービー #1: 0.07
最小 - 最大
-0.09494244 - 0.31092703
平均 (標準偏差)
-0.00031056 (±0.02028314)
対称性
空間群: 1
詳細
EMDB XML:
マップ形状
Axis order
X
Y
Z
Origin
0
0
0
サイズ
220
220
220
Spacing
220
220
220
セル
A=B=C: 493.89996 Å α=β=γ: 90.0 °
CCP4マップ ヘッダ情報:
mode
Image stored as Reals
Å/pix. X/Y/Z
2.245
2.245
2.245
M x/y/z
220
220
220
origin x/y/z
0.000
0.000
0.000
length x/y/z
493.900
493.900
493.900
α/β/γ
90.000
90.000
90.000
start NX/NY/NZ
0
0
-40
NX/NY/NZ
55
55
81
MAP C/R/S
1
2
3
start NC/NR/NS
0
0
0
NC/NR/NS
220
220
220
D min/max/mean
-0.095
0.311
-0.000
-
添付データ
-
試料の構成要素
-
全体 : CSFV IRES truncated from domain II, in complex with the Rabbit sm...
全体
名称: CSFV IRES truncated from domain II, in complex with the Rabbit small ribosomal 40S subunit and to DHX29
要素
試料: CSFV IRES truncated from domain II, in complex with the Rabbit small ribosomal 40S subunit and to DHX29
複合体: eukaryotic small ribosmal subunit
RNA: Internal Ribosomal Entry Site
タンパク質・ペプチド: DHX29
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超分子 #1000: CSFV IRES truncated from domain II, in complex with the Rabbit sm...
超分子
名称: CSFV IRES truncated from domain II, in complex with the Rabbit small ribosomal 40S subunit and to DHX29 タイプ: sample / ID: 1000 / 集合状態: one 40S, one CSFV IRES and one DHX29 / Number unique components: 3
凍結剤: ETHANE / チャンバー内湿度: 100 % / チャンバー内温度: 120 K / 装置: FEI VITROBOT MARK II 手法: 30 seconds waiting after sample deposition on the grid, blotting for seconds before plunging