Single-Cell Biophysics: Measurement, Modulation, and Modeling

Single-Cell Biophysics: Measurement, Modulation, and Modeling

Poster Abstracts

13-POS

Board 7

How Mrna Wraps the 30S at the Beginning of Translation

Yi-Lan Chen

, Jin-Der Wen

2,1

Genome and Systems Biology Degree Program, National Taiwan University and Academia

Sinica, Taipei, Taiwan,

Institute of Molecular and Cellular Biology, National Taiwan

University, Taipei, Taiwan.

Well begun is half done. In the cell, initiation is the rate limiting step in most protein synthesis

events. At the early stage of initiation, the prokaryotic 30S subunit of the ribosome binds to the

Shine-Dalgarno sequence of the mRNA, which then wraps around the 30S to form a pre-

initiation complex in the presence of the initiator tRNA. However, the detailed mechanisms in

this process are not clear. In order to see the dynamic signals between the 30S and mRNA, we

use single-molecule FRET and optical tweezers to observe the translation initiation in each state.

Here, we find that the mRNA reversibly wraps and unwraps around the 30S when the mRNA

contains a structure downstream to the initiation site, and the structure is partially destabilized by

the 30S during the wrapping-unwrapping process. Addition of the initiator tRNA opens some

weak downstream structures nearby and stably locks this pre-initiation complex to the correct

initiation site. In whole process, the initiation factors, IF1 and especially IF3 stabilize the binding

of mRNA. In this study, we present a method to observe the interaction of mRNA and the 30S

dynamically at the very beginning of translation which helps us to understand the mechanism of

translation initiation in more detail.