The Role of eIF4E Family Members in Zebrafish

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The translational initiation factor eIF4E is a central component in the initiation and regulation of translation in eukaryotic cells. Through its interaction with the 5' cap structure of mRNA and its translation partner, eIF4G, eIF4E functions to recruit mRNAs to the ribosome. The rapid accumulation of vertebrate EST and genome sequences has allowed the identification of multiple eIF4E family members. Based on sequence homologies and/or function, three classes of eIF4E have been recognized; Class I (archetypal eIF4E and sub-types), Class II (eIF4ELP/HP) and Class III (eIF4E-3, vertebrates only). The uncovering of multiple eIF4E related proteins suggests an unexpected complexity of the mRNA recruitment step and its regulation in vertebrates and has exemplified the difficulties in annotating DNA sequences on the basis of sequence homologies only. One hypothesis is that each form fills a specialized niche in the recruitment of capped mRNAs by the ribosome. Alternatively, it is possible that not all eIF4E family members function as initiation factors or in translational regulation directly, but in an unrelated function such as RNA/RNP export or RNA splicing. The overall goal of this project is to use the knowledge of eIF4E family members and unique reagents accumulated by the Jagus laboratory to elucidate their respective roles in the regulation of gene expression in higher eukaryotes. The objectives are to characterize the functions of eIF4E family members and determine their role in the regulation of gene expression through the following specific aims: 1) analysis of expression pattern of each family member in different tissues and at various developmental stages; 2) determination of the function of each eIF4E family member (from zebrafish and mammals) in translation using a variety of established assays; and 3) kinetic analyses of the interaction of each class with cap-structures, eIF4G and the 4EBPs.The production of cellular proteins begins with the template genetic code that is copied in the form of mRNA. The information encoded by mRNA is translated on the ribosomes into proteins. Control of the recruitment of mRNA by ribosomes is an important form of regulation of gene expression in animal cells. Several protein factors are required for the recruitment of mRNA by the ribosome, the most important of which is the translation factor eIF4E. eIF4E recognizes and binds to the cap structure at the 5' end of mRNA. The accumulation of DNA sequence data has allowed the Jagus laboratory to recognize three classes of eIF4E; Class I (prototypical eIF4E and sub-types), Class II (eIF4ELP/HP) and Class III (eIF4E-3, vertebrates only). The overall goal of this project is to characterize the functions of eIF4E family members and determine their role in the regulation of gene expression in the zebrafish developmental system.