Translation Initiation Factor IF3 Structure and Function

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

Abstract MCB-0079305 Simons SIMONS The ribosome is a complex molecular machine that faithfully translates information stored in the genetic code, into enzymes and other proteins. Understanding ribosome function has been and remains one of the most important challenges in molecular biology. The long-term goal of this project is to understand how the ribosome ensures translational accuracy (proper decoding) at its P-site. The P-site decodes information during translation initiation, and work spanning more that two decades has shown that translation initiation factor three (IF3) plays a crucial role in this event, almost certainly by modulating activities that are intrinsic to the ribosome itself. During the past 5 years, important new insights have emerged, including the three-dimensional structure of IF3 and the ribosome, visualization of the IF3/ribosome complex, and new insights into IF3 structure and function. IF3 is thought to operate at or close to the level of P-site function, most likely altering ribosome conformation and thereby the P-site. This modulation of P-site activity probably manifests itself in several seemingly unrelated IF3 effects. These developments hold great promise for an eventual understanding of P-site function and its modulation by IF3. However, before those important goals can be reasonably tackled, several basic and key aspects of IF3 structure and function must first be resolved. This project involves an integrated genetic and biochemical attack on several major unanswered questions at this level. The effects of key IF3 mutations will be examined with a powerful battery of assays designed to monitor IF3 function at several distinct levels of ribosome function. These efforts are instrumental in testing current models for IF3 modulation of ribosome function. IF3 determinants required for interaction with the ribosome will also be explored, and the IF3 binding determinants within the ribosome itself will be identified, in strategies based on existing experimental evidence. These studies are essential for an eventual understanding of how IF3 structure and function are integrated with that of the ribosome. In particular, this work will form a strong underpinning for studies that will eventually tackle IF3 function directly at the P-site.