线虫prg-1基因对小RNA表达的影响

以秀丽隐杆线虫为材料发现,prg-1基因突变不仅影响piRNA的表达,还影响部分miRNA的表达,同时还发现ncRNA-like型小RNA,对ncRNA-like序列比较,认为ncRNA-like与piRNA或miRNA序列极为相似;对ncRNA-like与miRNA或piRNA的基因座比较,发现ncRNA-like与miRNA或piRNA基因座完全相同．推测这些ncRNA-like型小RNA可能与miRNA或piRNA有着相同的RNA前体来源．     

A uniform system for microRNA annotation

MicroRNAs (miRNAs) are small noncoding RNA gene products about 22 nt long that are processed by Dicer from precursors with a characteristic hairpin secondary structure. Guidelines are presented for the identification and annotation of new miRNAs from diverse organisms, particularly so that miRNAs can be reliably distinguished from other RNAs such as small interfering RNAs. We describe specific criteria for the experimental verification of miRNAs, and conventions for naming miRNAs and miRNA genes. Finally, an online clearinghouse for miRNA gene name assignments is provided by the Rfam database of RNA families.     

Instability of miRNA and cDNAs derivatives in RNA preparations

Micro RNAs (miRNAs) are small RNA molecules, which function as important regulators of gene expression. We found that RNA preparation methods commonly utilized for miRNA expression studies yield highly unstable miRNAs. We studied the stability of four miRNAs belonging to different miRNAs families. A significant degradation of these molecules may be observed already three days after RNA isolation. Moreover, the respective cDNAs are highly unstable as well. Our findings indicate that instability of miRNAs and their cDNAs should be considered when designing miRNA expression studies.     

microRNAs - powerful repression comes from small RNAs

microRNAs (miRNAs) encode a novel class of small, non-coding RNAs that regulate gene expression post-trancriptionally. miRNAs comprise one of the major non-coding RNA families, whose diverse biological functions and unusual capacity for gene regulation have attracted enormous interests in the RNA world. Over the past 16 years, genetic, biochemical and computational approaches have greatly shaped the growth of the field, leading to the identification of thousands of miRNA genes in nearly all metazoans. The key molecular machinery for miRNA biogenesis and silencing has been identified, yet the precise biochemical and regulatory mechanisms still remain elusive. However, recent findings have shed new light on how miRNAs are generated and how they function to repress gene expression. miRNAs provide a paradigm for endogenous small RNAs that mediate gene silencing at a genome-wide level. The gene silencing mediated by these small RNAs constitutes a major component of gene regulation during various developmental and physiological processes. The accumulating knowledge about their biogenesis and gene silencing mechanism will add a new dimension to our understanding about the complex gene regulatory networks.     

The role of miRNAs and endogenous siRNAs in maternal‐to‐zygotic reprogramming and the establishment of pluripotency

RNA silencing is a complex of mechanisms that regulate gene expression through small RNA molecules. The microRNA (miRNA) pathway is the most common of these in mammals. Genome‐encoded miRNAs suppress translation in a sequence‐specific manner and facilitate shifts in gene expression during developmental transitions. Here, we discuss the role of miRNAs in oocyte‐to‐zygote transition and in the control of pluripotency. Existing data suggest a common principle involving miRNAs in defining pluripotent and differentiated cells. RNA silencing pathways also rapidly evolve, resulting in many unique features of RNA silencing in different taxonomic groups. This is exemplified in the mouse model of oocyte‐to‐zygote transition, in which the endogenous RNA interference pathway has acquired a novel role in regulating protein‐coding genes, while the miRNA pathway has become transiently suppressed.     

microPrimer: the biogenesis and function of microRNA

Discovered in nematodes in 1993, microRNAs (miRNAs) are non-coding RNAs that are related to small interfering RNAs (siRNAs), the small RNAs that guide RNA interference (RNAi). miRNAs sculpt gene expression profiles during plant and animal development. In fact, miRNAs may regulate as many as one-third of human genes. miRNAs are found only in plants and animals, and in the viruses that infect them. miRNAs function very much like siRNAs, but these two types of small RNAs can be distinguished by their distinct pathways for maturation and by the logic by which they regulate gene expression.     

Evolutionarily conserved function of a viral microRNA

MicroRNAs (miRNAs) are potent RNA regulators of gene expression. Some viruses encode miRNAs, most of unknown function. The majority of viral miRNAs are not conserved, and whether any have conserved functions remains unclear. Here, we report that two human polyomaviruses associated with serious disease in immunocompromised individuals, JC virus and BK virus, encode miRNAs with the same function as that of the monkey polyomavirus simian virus 40 miRNAs. These miRNAs are expressed late during infection to autoregulate early gene expression. We show that the miRNAs generated from both arms of the pre-miRNA hairpin are active at directing the cleavage of the early mRNAs. This finding suggests that despite multiple differences in the miRNA seed regions, the primary target (the early mRNAs) and function (the downregulation of early gene expression) are evolutionarily conserved among the primate polyomavirus-encoded miRNAs. Furthermore, we show that these miRNAs are expressed in individuals diagnosed with polyomavirus-associated disease, suggesting their potential as targets for therapeutic intervention.     

Extracellular small RNAs: what, where, why?

miRNAs (microRNAs) are a class of small RNA that regulate gene expression by binding to mRNAs and modulating the precise amount of proteins that get expressed in a cell at a given time. This form of gene regulation plays an important role in developmental systems and is critical for the proper function of numerous biological pathways. Although miRNAs exert their functions inside the cell, these and other classes of RNA are found in body fluids in a cell-free form that is resistant to degradation by RNases. A broad range of cell types have also been shown to secrete miRNAs in association with components of the RISC (RNA-induced silencing complex) and/or encapsulation within vesicles, which can be taken up by other cells. In the present paper, we provide an overview of the properties of extracellular miRNAs in relation to their capacity as biomarkers, stability against degradation and mediators of cell-cell communication.