| Budget Amount *help |
¥4,150,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥450,000)
Fiscal Year 2007: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Fiscal Year 2006: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
In the course of study on the posttranscriptional regulation of the Arabidopsis CGS1 gene, which encodes the key enzyme of methionine biosynthesis, we have found that the nascent CGS1 peptide mediates its own translation elongation arrest in response to S-adenosylmethionine, a metabolite of methionine. Although several examples of nascent peptide-mediated ribosomal regulations have been reported in eukaryotes, all other regulatory nascent peptides are encoded by upstream ORFs (uORF) located in the 5'UTR, except for the CGS1 gene. In these systems, uORF-encoded peptides cause ribosome stalling, resulting in downregulation of translation of the main ORF.
In order to identify new Arabidopsis genes that are regulated by nascent peptide, we screened for uORF-containing genes from Arabidopsis full-length cDNA database, and tested their amino acid-sequence dependency of the effect on translation of the main ORF by using transient assay with Arabidopsis protoplasts. From this screen, a frameshift mutation of one uORF was found to cause upregulation of the main ORF. Alanine scanning analysis showed that C-terminal part of the peptide encoded by this uORF is important for the regulation. In contrast, a frameshift mutation of another uORF caused downregulation of the main ORF.
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