Structural Studies on the eIF4A-eIF4G Interaction in Translation Initiation

Abstract

Protein synthesis is an important cellular process, and the RNA helicase eIF4A plays a vital role in unwinding messenger RNA and scanning during translation initiation. eIF4A has little activity in isolation, but is modulated by other initiation factors such as eIF4G and eIF4H. In this thesis, we explore how these proteins come together to form a functional unwinding complex. We begin with the NMR solution structure of a single domain from this complex, eIF4G HEAT2. We then map interactions involving HEAT2 and its binding partners, as well as those involving the N-terminal domain of eIF4A. We use this information first to construct a structure of the two-domain complex of HEAT2 and eIF4A-NTD, and expand this work toward the structure of the 70kDa, three-domain complex of HEAT2 with full-length eIF4A. Finally, we incorporate eIF4H and another domain of eIF4G to model the entire functional complex, and explore how interactions between domains rearrange upon binding, hydrolysis, and release of ATP. These results give us a better understanding of how eIF4G modulates eIF4A helicase activity. Moreover, the domain organization of the complex allows us to construct a more compelling model to explain how eIF4A facilitates preinitiation complex scanning along a messenger RNA.