The Roles of eIF4G and Associated Factors in Ribosomal Attachment and Scanning During Translation Initiation

eIF4G 及相关因素在翻译起始过程中核糖体附着和扫描中的作用

• 批准号: 0110834
• 负责人: Christopher Hellen
• 金额: $ 27万
• 依托单位: SUNY Health Science Center at Brooklyn
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2004-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0110834&HistoricalAwards=false
• 关键词: Roles; eIF4G; Associated; Factors; Ribosomal

Eukaryotic initiation factor (eIF) 4G coordinates ribosomal binding and subsequent ribosomalscanning on the 5'NTR of an mRNA by binding to factors that are required for both steps. eIF4G is asubunit of eIF4F, which also has eIF4E (cap-binding protein) and eIF4A (helicase) subunits. This projectwill characterize the roles of eIF4G and associated factors in these two stages of initiation using mRNAsthat depend on either the 5'-terminal cap or an internal ribosomal entry site (IRES) for ribosomalbinding. Loading of the 40S ribosomal subunit onto mRNA may involve local unwinding of mRNA bybound eIF4F and interaction between eIF4G and ribosome-associated eIF3. The roles of eIF4G'sinteractions with RNA, eIF4A and eIF3 in ribosomal attachment and scanning will be characterized byintegrating biochemical assays (such as eIF4G's influence on eIF4A's helicase activity) withreconstitution of initiation on model mRNAs. The role of Ded1p, another RNA helicase that has beenimplicated in scanning will also be characterized. Initiation on the encephalomyocarditis virus (EMCV)IRES requires specific binding by eIF4G/4A. The mechanisms of recognition of this IRES by eIF4G/4A, ofenhancement of binding of eIF4G/4A to related IRESs by specific IRES trans-acting factors, and ofpromotion of ribosomal attachment by the eIF4G/4A/IRES complex will be determined. The cap-bindingactivity of eIF4F is down-regulated during mitosis and apoptosis when some cellular IRES-containingmRNAs remain active. The hypothesis that these IRESs resemble EMCV in interacting with eIF4G/4A topromote ribosomal binding when eIF4E is inactive will be tested. These studies will provide insightsinto mechanisms for selective translation of specific mRNAs.

真核起始因子（eIF） 4G通过与两个步骤所需的因子结合，协调核糖体结合和随后在mRNA的5'NTR上的核糖体扫描。eIF4G是eIF4F的亚基，eIF4F也有eIF4E（帽结合蛋白）和eIF4A（解旋酶）亚基。该项目将使用依赖于5'端帽或核糖体内部进入位点（IRES）的mrna来表征eIF4G和相关因子在这两个起始阶段的作用。将40S核糖体亚基装载到mRNA上可能涉及结合eIF4F的mRNA的局部解绕以及eIF4G与核糖体相关的eIF3之间的相互作用。eIF4G与RNA、eIF4A和eIF3的相互作用在核糖体附着和扫描中的作用将通过整合生化分析（如eIF4G对eIF4A解旋酶活性的影响）和模型mrna的起始重构来表征。另一种与扫描有关的RNA解旋酶Ded1p的作用也将被描述。脑心肌炎病毒（EMCV）IRES的启动需要eIF4G/4A的特异性结合。eIF4G/4A识别该IRES的机制、特定IRES作用因子增强eIF4G/4A与相关IRES的结合以及eIF4G/4A/IRES复合物促进核糖体附着的机制将被确定。在有丝分裂和凋亡过程中，当一些细胞ires - mrna保持活性时，eIF4F的帽结合活性被下调。当eIF4E失活时，这些IRESs类似EMCV与eIF4G/4A相互作用以促进核糖体结合的假设将被验证。这些研究将为特定mrna的选择性翻译机制提供见解。