[대학원 생명과학과 세미나 안내]
연사 : 이중원 박사 (유틸렉스(Eutilex Co., Ltd.))
연제 : A structural requirement for ribosome binding by the Ltn1 E3 ligase uncovered through in vitro reconstitution of co-translational quality control
일시 : 2016년 9월 2일 (금) 오후 4시
장소 : 하나과학관 A동 109호
초청교수 : 송현규 교수
Abstract
The Listerin/Ltn1 E3 ligase has emerged as a paradigm for understanding co‐.translational
ubiquitylation. Ltn1 is associated with ribosomes and ubiquitylates nascent polypeptides that
become stalled during synthesis; among Ltn1’s substrates are aberrant products of mRNA
lacking stop codons (“non‐top translation products,” or NSPs). Here we report the
reconstitution of NSP ubiquitylation in Neurospora crassa cell extracts. Upon translation in
vitro, NSPs became stalled in ribosomes and were ubiquitylated in a Ltn1‐dependent manner.
We show that ubiquitylation happened while NSPs were still ribosome‐associated, and
stimulated NSP release. Furthermore, by reconstituting reactions using Ltn1‐deficient extracts
supplemented with recombinant wild type or mutant Ltn1, we demonstrate that the conserved
N‐terminal domain (NTD) was critical for Ltn1 binding to ribosomes, and that Ltn1 NTD
mutants defective in ribosome binding also exhibited impaired NSP ubiquitylation. Our
findings are consistent with a model in which Ltn1 utilizes ribosomes as adapters to target
NSPs for ubiquitylation.