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首页> 外文期刊>Molecular and Cellular Biology >Degradation of the soybean ribulose-1,5-bisphosphate carboxylase small-subunit mRNA, SRS4, initiates with endonucleolytic cleavage.
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Degradation of the soybean ribulose-1,5-bisphosphate carboxylase small-subunit mRNA, SRS4, initiates with endonucleolytic cleavage.

机译：大豆核糖-1,5-二磷酸羧化酶小亚基mRNA SRS4的降解始于核酸内切酶裂解。

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摘要

The degradation of the soybean SRS4 mRNA, which encodes the small subunit of ribulose-1,5-bisphosphate carboxylase, yields a set of proximal (5' intact) and distal (3' intact) products both in vivo and in vitro. These products are generated by endonucleolytic cleavages that occur essentially in a random order, although some products are produced more rapidly than others. Comparison of sizes of products on Northern (RNA) blots showed that the combined sizes of pairs of proximal and distal products form contiguous full-length SRS4 mRNAs. When the 3' ends of the proximal products and the 5' ends of the distal products were mapped by S1 nuclease and primer extension assays, respectively, both sets of ends mapped to the same sequences within the SRS4 mRNA. A small in vitro-synthesized RNA fragment containing one cleavage site inhibited cleavage of all major sites, equivalently consistent with one enzymatic activity generating the endonucleolytic cleavage products. These products were rich in GU nucleotides, but no obvious consensus sequence was found among several cleavage sites. Preliminary evidence suggested that secondary structure could play a role in site selection. The structures of the 5' ends of the proximal products and the 3' ends of the distal products were examined. Proximal products were found with approximately equal frequency in both m7G cap(+) and m7G cap(-) fractions, suggesting that the endonucleolytic cleavage events occurred independently of the removal of the 5' cap structure. Distal products were distributed among fractions with poly(A) tails ranging from undetectable to greater than 100 nucleotides in length, suggesting that the endonucleolytic cleavage events occurred independently of poly(A) tail shortening. Together, these data support a stochastic endonuclease model in which an endonucleolytic cleavage event is the initial step in SRS4 mRNA degradation.
机译：编码大豆核糖-1,5-双磷酸羧化酶小亚基的大豆SRS4 mRNA的降解在体内和体外产生了一组近端（完整的5'）和远端（完整的3'）产品。这些产物是通过基本上以随机顺序发生的核酸内切裂解产生的，尽管某些产物的产生比其他产物更快。 Northern（RNA）印迹上产物大小的比较表明，近端和远端产物对的组合大小形成了连续的全长SRS4 mRNA。当分别通过S1核酸酶和引物延伸分析法绘制近端产物的3'末端和远端产物的5'末端时，两组末端均映射到SRS4 mRNA中的相同序列。含有一个切割位点的体外合成小RNA片段可抑制所有主要位点的切割，与产生内切核酸裂解产物的一种酶活性等效。这些产物富含GU核苷酸，但是在几个切割位点之间没有发现明显的共有序列。初步证据表明，二级结构可能在位点选择中起作用。检查了近端产品的5'端和远端产品的3'端的结构。在m7G cap（+）和m7G cap（-）馏分中发现近端产物的频率大致相等，这表明发生内切核酸裂解事件的发生与5'cap结构的去除无关。远端产物分布在聚（A）尾巴的各个部分之间，长度范围从无法检测到长度大于100个核苷酸，这表明内切核酸裂解事件独立于聚（A）尾巴缩短而发生。总之，这些数据支持了一种随机内切核酸酶模型，其中内切核酸裂解事件是SRS4 mRNA降解的第一步。

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