【作者】 吴磊；

【导师】 陶士珩；

【作者基本信息】 西北农林科技大学 ， 生物信息学， 2011， 硕士

【摘要】 MiRNA是真核生物细胞内长约20²5个核苷酸大小的单链RNA分子片段。它在进化中呈现出序列保守性。截至现在,miRNA在近1000种物种中都已报道。它在生命活动中参与各种各样的调节途径,发挥着重要的调控作用,包括器官形成、发育、病毒防御、造血过程、细胞增殖和凋亡、脂肪代谢等等。MiRNA是经过一系列核酸酶的剪切加工从较长的初级转录体变成非编码的小分子RNA,经过碱基互补配对的方式识别靶基因mRNA,并根据互补程度的高低指导沉默复合体降解靶mRNA或者阻遏靶mRNA的翻译。MiRNA近年来一直是生物学研究的热点,但它的很多作用过程仍未被阐明。本文从已报告的miRNA和它们前体上的某些重要位点入手,通过生物统计学方法探索miRNAs保守性等规律,为证明保守性在miRNAs的成熟过程中的作用和从信息熵角度理解miRNA前体的一级结构提供一些依据。本实验把动物、植物和病毒分成三类,每类又分为四组,通过计算单个碱基信息的冗余度（D₁（L））和相邻碱基相关信息冗余（D₂（L））,即信息熵方法研究分析已报告的miRNA和它们前体上的一些重要位点,对miRNA前体的一级结构从信息熵角度进行阐释。实验结果显示,尽管在各个组里(D₁（L）和D₂（L）值的变化基本呈正相关趋势,但相邻碱基相关信息冗余度比单个碱基信息的冗余度包含更多的信息。这些关键位点上,动物的前体miRNA比来源于植物的前体miRNA保守性差。该现象表明保守性可能参与了Dicer酶的识别和剪切过程,其在动物miRNAs的成熟过程中起着举足轻重的作用。更多还原

【Abstract】 MiRNA is a kind of single-stranded RNA molecules with the length from 20 to 25 nucleotides in eukaryotic cell. It shows evolutionary sequence conservation. Up to data, miRNAs have been reported in nearly 1000 species. It plays various roles in life activities, including organ formation, development, viral defence, hematopoiesis, cell proliferation and apoptosis, fat metabolism and so on. MiRNA is produced by a series of shear processing nuclease from longer primary transcripts into small molecules of non-coding RNA. It functions in means of complementary base pairing with targetable mRNA, and the degree of complementarity guides either the silencing complex or just repression of targetable mRNA.Though studing in miRNA has been always as a hot spot in biological research recently, how it functions in the biological process is still an open question. This paper has studied on miRNAs and their precursors, and some of the important sites were analyzed by exploring bio-statistical method to prove the importance of the conservatism in miRNAs’ formation and lies a hypothesis on the primary structure of the precursor.In this study, animals, plants and viruses were divided into three categories, and each category was even subdivided into four groups, by calculating the single base of information redundancy （D₁ （L）） and the adjacent base information redundancy （D₂ （L） ）. Information entropy analysis has been reported on miRNA and their precursors, and some of the important sites of the primary structure of miRNA precursors were studied, and based on the perspective, the interpretation of information entropy was elaborated for the miRNA formations.The results showed that the adjacent base information redundancy of information contains more information than a single base, despite the various groups in the (D₁ （L） and D₂ （L） value was positively correlated with changes in the basic trend. These important positions in animal is less conservative than that in plants. The sequence conservatism in some positions shows that some positions are important in the Dicer enzyme process, identifying and cutting the precursors, especially in animals.更多还原