Mobile microRNAs hit the target

MicroRNAs (miRNAs) are negative regulators of gene expression in eukaryotic organisms, whereas small interfering RNAs (siRNAs) guide host-cell defence against viruses, transposons and transgenes. A key issue in plant biology is whether miRNAs act only in cells in which they are formed, or if, like siRNAs, they also function after passive diffusion or active transportation into other cells. Recent reports show that miRNAs are indeed able to move between plant cells to direct developmental programming of gene expression. In both leaf and root development, miRNAs establish intercellular gradients of gene expression that are essential for cell and tissue differentiation. Gradients in gene expression also play crucial roles in animal development, and there is strong evidence for intercellular movement of miRNAs in animals. Thus, intercellular movement of miRNAs may be crucial to animal developmental biology as well as plants.     

MicroRNAs对动物皮肤和毛发发育调控作用的研究进展

MicroRNAs是近年来发现的一类由19-25个核苷酸组成的非编码单链小RNA分子,它们通过与靶基因mRNA3’UTR结合抑制靶基因的翻译,在转录后水平调控基因表达.MicroRNAs参与了包括细胞分化、增殖和凋亡及免疫系统应答在内的一系列发育调控和生物学过程.最近研究发现MicroRNAs在多种哺乳动物皮肤中均表达,并参与了哺乳动物皮肤及毛发发育的调控过程,这些都为研究这个新颖的调控因子在干细胞生物学和发育生物学中的功能奠定了基础.本文综述了近年来MicroRNAs对哺乳动物皮肤和毛发发育调控作用的研究状况.     

植物microRNAs研究进展

植物microRNAs(miRNAs)是一类与RNA诱导沉默复合体相关的约由22个核苷酸组成的单链小RNA分子, 其主要功能是, 通过特异性剪切靶mRNA或阻遏靶mRNA的正常翻译在转录后水平调控基因的负表达。植物miRNAs的靶标主要是参与调控植物生长发育和防御应答的转录因子家族。文章主要综述miRNAs在植物体内的生物发生、作用机制及其调控作用研究新进展。     

miRNP:mRNA association in polyribosomes in a human neuronal cell line

MicroRNAs (miRNAs) are small regulatory RNAs that control gene expression by base-pairing with their mRNA targets. miRNAs assemble into ribonucleoprotein complexes termed miRNPs. Animal miRNAs recognize their mRNA targets via partial antisense complementarity and repress mRNA translation at a step after translation initiation. How animal miRNAs recognize their mRNA targets and how they control their translation is unknown. Here we describe that in a human neuronal cell line, the miRNP proteins eIF2C2 (a member of the Argonaute family of proteins), Gemin3, and Gemin4 along with miRNAs cosediment with polyribosomes. Furthermore, we describe a physical association between a let-7b (miRNA)-containing miRNP and its putative human mRNA target in polyribosome-containing fractions. These findings suggest that miRNP proteins may play important roles in target mRNA recognition and translational repression.     

植物MicroRNA的特点与研究方法

MicroRNAs(miRNAs)是一类在植物、动物、单细胞藻类和病毒等中存在的具有调控基因表达作用的内源非编码小RNA(small RNAs).在植物中,miRNAs主要依靠与靶基因之间完全或近乎完全的互补配对切割靶基因或翻译抑制实现其调控功能.主要综述植物miRNA的特点,并介绍miRNA的获得方式、靶基因预测及验证方法.     

Detecting microRNA activity from gene expression data

Background  

MicroRNAs (miRNAs) are non-coding RNAs that regulate gene expression by binding to the messenger RNA (mRNA) of protein coding genes. They control gene expression by either inhibiting translation or inducing mRNA degradation. A number of computational techniques have been developed to identify the targets of miRNAs. In this study we used predicted miRNA-gene interactions to analyse mRNA gene expression microarray data to predict miRNAs associated with particular diseases or conditions.     

Systematic study of cis-antisense miRNAs in animal species reveals miR-3661 to target PPP2CA in human cells

MicroRNAs (miRNAs) suppress targeting gene expression through blocking translation or triggering mRNA degradation and, in general, act in trans, through a partially complementary interaction with the 3′ untranslated region (3′ UTR) or coding regions of a target gene. Although it has been reported previously that some miRNAs suppress their target genes on the opposite strand with a fully complementary sequence (i.e., natural antisense miRNAs that act in cis), there is no report to systematically study such cis-antisense miRNAs in different animal species. Here we report that cis-antisense miRNAs do exist in different animal species: 48 in Caenorhabditis elegans, 17 in Drosophila, 36 in Mus musculus, and 52 in Homo sapiens using a systematical bioinformatics approach. We show that most of these cis-antisense miRNAs can efficiently reduce the expression levels of their target genes in human cells. We further investigate hsa-miR-3661, one of the predicted cis-antisense miRNAs, in detail and demonstrate that this miRNA directly targets the coding sequence of PPP2CA located on the opposite DNA strand and inhibits the PPP2CA expression. Taken together, these results indicate that cis-antisense miRNAs are conservative and functional in animal species including humans.