Autoregulation of the gene for cystathionine γ-synthase in arabidopsis:: post-transcriptional regulation induced by S-adenosylmethionine
Autoregulation of the gene for cystathionine γ-synthase in arabidopsis:: post-transcriptional regulation induced by S-adenosylmethionine
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DOI：
10.1042/bst0320597
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发表时间：
2004-08-01
影响因子：
3.9
通讯作者：
Naito, S
中科院分区：
文献类型：
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作者：
Onouchi, H;Lambein, I;Naito, S
胱硫醚γ-合酶（CGS）是高等植物蛋氨酸生物合成的第一个关键步骤。CGS由拟南芥中的CGS 1基因编码。CGS 1 mRNA的稳定性在蛋氨酸应用中下调，CGS 1本身的外显子1编码区对这种调节是必要的和足够的。拟南芥的mto 1突变体在CGS 1外显子1内携带单个氨基酸序列改变，这种调节缺陷并过度积累甲硫氨酸。由于CGS 1外显子1在此调节过程中的顺式作用，我们提出了一个模型，即在CGS 1 mRNA的翻译过程中发生的调节时，新生的多肽的CGS和它的mRNA是非常接近的。事实上，翻译抑制剂放线菌酮的应用在体内消除了这种调节。该模型预测，该调节可以在体外翻译系统中再现。使用小麦胚芽提取物的体外翻译系统的研究表明，S-腺苷甲硫氨酸，甲硫氨酸的直接代谢产物，是这种调节的效应。在体外检测到一种可能是CGS 1 mRNA在体内降解中间产物的5 ′截短RNA，表明小麦胚体外翻译系统反映了CGS 1 mRNA的体内调控。
Cystathionine gamma-synthase (CGS) catalyses the first committed step of methionine biosynthesis in higher plants. CGS is encoded by the CGS1 gene in Arabidopsis. Stability of CGS1 mRNA is down-regulated in response to methionine application and the exon 1-coding region of CGS1 itself is necessary and sufficient for this regulation. mto1 (for (m) under bare (t) under bar hionine (o) under bar veraccumulation) mutants of Arabidopsis, which carry single amino-acid sequence alterations within CGS1 exon 1, a re deficient in this regulation and overaccumulate methionine. Since CGS1 exon 1 acts in cis during this regulation, we have proposed a model that the regulation occurs during translation of CGS1 mRNA when the nascent polypeptide of CGS and its mRNA are in close proximity. in fact, application of the translation inhibitor cycloheximide abolished this regulation in vivo. This model predicts that the regulation can be reproduced in an in vitro translation system. Studies using the in vitro translation system of wheatgerm extract have indicated that S-adenosylmethionine, a direct metabolite of methionine, is the effector of this regulation. A 5'-truncated RNA species, which is a probable degradation intermediate of CGS1 mRNA in vivo, was also detected in vitro, suggesting that the wheatgerm in vitro translation system reflects the in vivo regulation.