Jagus MCB 9808401 1. Technical The aim of this study is to characterize the function(s) of a novel protein that shares homology with the translational initiation factor eIF4E. The goal is to establish the role(s) of the protein in the regulation of mRNA recruitment. The experimental strategy is designed to determine whether this eIF4E-like protein (4E-LP) stimulates or inhibits the recruitment of mRNAs for translation and identify the proteins with which 4E-LP interacts to perform its function(s). This will extend our understanding of the control of gene expression at this important step. cDNA sequences have been established for human, mouse and zebrafish 4E-LP. Sequence comparisons have shown the 4E-LP is present in a wide range of animal and plant species and is highly conserved. Northern analysis has shown that the mRNA for 4E-LP is present in all tissues tested to date and is under regulation during early development. Similarly, the protein appears to be in all tissues tested, although at a lower level than eIF4E. Like eIF4E, 4E-LP can bind cap structures and interact with eIF4G. Unlike eIF4E, 4E-LP does not have the regulatory phosphorylation site at the carboxy-terminus. It remains to be determined whether the role of 4E-LP is that of an alternate initiation factor which facilitates the translation of specific mRNAs (or all mRNAs under specific physiological conditions), or whether the protein functions in a regulatory capacity to modulate the activity of eIF4E (by competing with eIF4E interacting proteins). The developmental regulation which suggests a role for 4E-LP in the regulation of gene expression during early development, is investigated in the zebrafish developmental model, from which eIF4E and eIF4G have been obtained. eIF4E plays a pivotal role in the regulation of gene expression by controlling mRNA recruitment. eIF4E recruits RNAs by binding to the 5' m7Gppp cap structure. The activity of eIF4E is highly regulated and the factor has been shown to be a major t arget of signals transduced from growth factor receptors and proto-oncogenes. eIF4E functions in conjunction with eIF4G, to which it binds. Together these factors recruit mRNAs to the ribosomes for translation. The regulation of the recruitment of mRNAs by eIF4E and eIF4G is regulated by the MAP kinase and rapamycin-sensitive signalling pathways which control phosphorylation of eIF4E and the regulatory eIF4E binding protein 1, 4E-BP1. Regulation of eIF4E/4G function can also occur through the intervention of proteins that share homology with eIF4G. These proteins either encroach upon the interaction of eIF4E with eIF4G (eIF4E binding proteins or 4E-BPs) or sequester other initiation factors required for the recruitment of mRNA (NAT1, DAP-5, or p97). The discovery of 4E-LP adds yet another facet to the regulation of mRNA recruitment and has implications for the regulation of diverse cellular functions. Jagus 2. Non-technical 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. Loss of control of this step can lead to developmental abnormalities and the loss of growth control. 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. eIF4E is under heavy regulation by reversible modification (phosphorylation) and by interaction with other proteins. The aim of this study is to characterize a novel protein, 4E-LP, that shares homology with eIF4E. The mRNA encoding 4E-LP is present in all tissues tested and is under regulation during early development. Like eIF4E, 4E-LP can bind to cap structures and interact with other components of translation. The big question is whether it function as an eIF4E look-alike or as a competitive inhibitor of eIF4E function. The developmental significance of 4E-LP will be investigated in zebrafish developmepmental systems.
of translation. The big questio n is whether it functions as an eIF4E look-alike or as a competive inhibitor of eIF4E function. The developmental significance of 4E-LP will be investigated in the zebrafish developmental system. Jagus, R., Ph.D. A. PROJECT SUMMARY 4 Jagus, R. C. PROJECT DESCRIPTION NSF FORM 1360 (1/94) 5
