Regulation of RNA degradation by RNase

在s -腺苷甲硫氨酸（SAM）存在下，拟南芥胱硫氨酸γ -合成酶（CGS） mRNA在体外翻译时，在Ser-94位点诱导翻译阻滞，进而诱导CGS mRNA降解。通过体外翻译制备了携带CGS第一外显子编码区的mRNA，并将其用于小麦胚芽提取物的体外翻译编程。核糖体在易位阶段被阻滞，翻译中间体肽基trna位于a位点。鉴定出一系列mRNA降解中间体，其5'端彼此相距约30个核苷酸。发现的证据表明，这些降解中间体对应于堆积在初始停滞核糖体后面的核糖体。Poly (G)在小麦胚芽提取物的体外翻译系统中具有抑制RNase活性的作用。当Poly(G)加入到翻译反应混合物中时，CGS mRNA的一个5‘片段，其3’端与降解中间体的一个5'端匹配。结果表明，mRNA的降解是通过核糖核内溶解消化发生的。大肠杆菌核酸酶大肠杆菌素E5可消化trna的反密码子环，包括trna中的trna， trna中的trna。Colicin E5优先消化GU二核苷酸。研究了大肠杆菌素E5的结构与底物特异性关系。底物特异性可以用底物袋处的结构约束来解释。分析了消化tRNA（Arg）的大肠杆菌素D在出芽酵母和HeLa细胞中表达的影响。

When cystathionine gamma-synthase (CGS) mRNA of Arabidopsis is translated in vitro in the presence of S-adenosylmethionine (SAM), translation arrest is induced at Ser-94, which then induces CGS mRNA degradation. mRNA that carries the first exon coding region of CGS was prepared by in vitro translation and was used to program in vitro translation of wheat germ extract. Ribosome was stalled at the step of translocation and the peptidyl-tRNA, the translation intermediate, was located in the A-site. A series of mRNA degradation intermediates, whose 5' ends were separated by about 30 nucleotides from each other, were identified. Evidence was found that shows that these degradation intermediates correspond to ribosomes that were stacked behind the initial stalled ribosome. Poly (G) has been reported to inhibit RNase activity in the in vitro translation system of wheat germ extract. When Poly(G) was added to the translation reaction mixture, a 5'-fragment of CGS mRNA whose 3' end matches with one of the 5' -ends of the degradation intermediate. The result suggested that the mRNA degradation occurs by an endoribonucleolytic digestion.An Escherichia coli ribonuclease colicin E5 digests the anticodon loop of tRNAs for Trp, His, Asn and Asp. Colicin E5 preferentially digests GU dinucleotide. Structure and substrate specificity relationship of colicin E5 were studied. The substrate specificity could be explained by the structural constraints at the substrate pocket. Effects of expression of colicin D that digests tRNA(Arg) in budding yeast and HeLa cells were analyzed.