Functional aspects of animal microRNAs

MicroRNAs (miRNAs) are a recently discovered family of small regulatory molecules that function by modulating protein production. There are approximately 500 known mammalian miRNA genes, and each miRNA may regulate hundreds of different protein-coding genes. Mature miRNAs bind to target mRNAs in a protein complex known as the miRNA-induced silencing complex (miRISC), sometimes referred to as the miRNP (miRNA-containing ribonucleoprotein particles), where mRNA translation is inhibited or mRNA is degraded. These actions of miRNAs have been shown to regulate several developmental and physiological processes including stem cell differentiation, haematopoiesis, cardiac and skeletal muscle development, neurogenesis, insulin secretion, cholesterol metabolism and the immune response. Furthermore, aberrant expression has been implicated in a number of diseases including cancer and heart disease. The role of miRNAs in these developmental, physiological and pathological processes will be reviewed. Received 3 August 2007; received after revision 3 October 2007; accepted 5 October 2007     

Evidence that miRNAs are different from other RNAs

An examination of 513 known pre-miRNAs and 237 other RNAs (tRNA, rRNA, and mRNA) revealed that miRNAs were significantly different from other RNAs (p < 0.001). miRNA genes were less conserved than other RNA genes, although their mature miRNA sequences were highly conserved. The A+U content of pre-miRNAs was higher than non-coding RNA (p < 0.001), but lower than mRNAs. The nucleotides in pre-miRNAs formed more hydrogen bonds and base pairs than in other RNAs. miRNAs had higher negative adjusted minimal folding free energies than other RNAs except tRNAs (p < 0.001). The MFE index (MFEI) was a sufficient criterion to distinguish miRNAs from all coding and non-coding RNAs (p < 0.001). The MFEI for miRNAs was 0.97, significantly higher than tRNAs (0.64), rRNAs (0.59), or mRNAs (0.65). Our findings should facilitate the prediction and identification of new miRNAs using computational and experimental strategies. Received 5 October 2005; received after revision 4 November 2005; accepted 16 November 2005     

大豆降解组文库microRNAs的启动子分析

研究目的：创新要点：通过分析miRNA的核心启动子和顺式作用元件为进一步解析大豆（Glycinemax）miRNAs表达调控及其功能研究提供重要信息。利用生物信息学方法全面解析了大豆降解组文库miRNA的启动子特征,并依据顺式作用元件及靶基因构建了miRNA的表达与生长素响应因子、赤霉素响应因子之问存在潜在的负反馈调控网络。研究方法：本研究利用TSSP程序和PlantCARE数据库预测了来自大豆降解组文库的440个miRNA的核心启动子以及369个miRNAs的顺式作用元件,并依据顺式作用元件及靶基因构建miRNA调控网络。重要结论：83．86％的miRNA在其上游序列中含有启动子,8．64％的miRNA在其下游序列中含有启动子,21．59％的miRNA包含增强子。核心启动子的TATA盒与转录起始位点（TSSs）的分布相似（见图2）。此外,对转录起始位点5’端的顺式作用元件预测为miRNAs的可能功能和表达的时空性提供了线索。miRNAs的顺式作用元件和靶基因的分析显示,部分miRNA的表达与生长素响应因子、赤霉素响应因子之间存在潜在的负反馈调控（见图3）。     

microRNAs 的SNPs研究进展

miRNAs是一类重要的基因调节因子,已有的研究表明它在生物体发育、细胞增殖、凋亡、脂类代谢、激素分泌以及肿瘤发生等多种生理和病理过程中发挥重要作用。本文通过对pre-miRNAs、成熟miRNAs、miRNAs的靶基因以及畜禽miRNAs的SNP的研究情况进行综述,对miRNAs的SNP在未来可能的为人类疾病治疗、提高畜禽生产性能方面的作用进行思考。