2006 Fiscal Year Final Research Report Summary
Molecular mechanism of translation arrest and mRNA degradation in cystathionine gamma-synthase, the key-step enzyme of methionine biosynthesis.
| Project/Area Number |
16370016
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
植物生理・分子
|
|---|
| Research Institution | HOKKAIDO UNIVERSITY |
|---|
Principal Investigator |
NAITO Satoshi Hokkaido Univ., Faculty of Advanced Life Science, Prof., 大学院先端生命科学研究院, 教授 (20164105)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
ONOUCHI Hitoshi Hokkaido Univ., Research Faculty of Agr., Assoc.Prof., 大学院農学研究院, 助教授 (50322839)
|
|---|
| Project Period (FY) |
2004 – 2006
|
| Keywords | Metabolic regulation / Cystathionine gamma-synthase / S-Adenosylmethionine / Methionine / mRNA degradation / Arabidopsis / Mutations |
|---|
| Research Abstract |
Cystathionine gamma-synthase (CGS) of Arabidopsis catalyzes the key step in methionine biosynthesis. Unlike many of the key-step enzymes in biosynthetic pathways, CGS is not an allosteric enzyme. Expression of CGS is feedback-regulated at the step of mRNA degradation and S-adenosylmethionine (SAM) acts as the effector. Upon mRNA degradation, 5'-truncated RNA species are formed as degradation intermediates. A short stretch of amino acids, termed the MTO1 region, located within the first exon-coding region of CGS itself, functions as the cis element in this regulation. CGS regulation occurs during translation and is reproduced in the in vitro translation system of wheat germ extract. Studies using the in vitro system revealed that, prior to the mRNA degradation, SAM induces translation elongation arrest at around the MTO1 region. Thus, translation elongation arrest triggers the mRNA degradation. Finer mapping of the translation arrest site showed that translation arrest occurs at Ser-94 located right after the MTO1 region, and peptidyl-tRNA(Ser) accumulates. Alanine substitution experiments identified that, in addition to the MTO1 region amino acid sequence, Trp-93 and Ser-94 are important for the translation arrest. A nascent peptide emerges from the translating ribosome through the ribosomal exit tunnel. This exit tunnel is 15-20 Angstroms in diameter and about 100 Angstroms long, and 30-40 amino acid residues of the nascent peptide will be located in the tunnel. Relative positions of the MTO1 region and the arrest site (Ser-94) suggest that the MTO1 region nascent peptide is located within the exit tunnel. For genetic analyses of the CGS regulation, Arabidopsis mutants that alter the post-transcriptional regulation of CGS expression were isolated and their responsive genes have been identified.
|
Research Products
(6 results)
