Widespread translational inhibition by plant miRNAs and siRNAs

High complementarity between plant microRNAs (miRNAs) and their messenger RNA targets is thought to cause silencing, prevalently by endonucleolytic cleavage. We have isolated Arabidopsis mutants defective in miRNA action. Their analysis provides evidence that plant miRNA-guided silencing has a widespread translational inhibitory component that is genetically separable from endonucleolytic cleavage. We further show that the same is true of silencing mediated by small interfering RNA (siRNA) populations. Translational repression is effected in part by the ARGONAUTE proteins AGO1 and AGO10. It also requires the activity of the microtubule-severing enzyme katanin, implicating cytoskeleton dynamics in miRNA action, as recently suggested from animal studies. Also as in animals, the decapping component VARICOSE (VCS)/Ge-1 is required for translational repression by miRNAs, which suggests that the underlying mechanisms in the two kingdoms are related.     

Redirection of filial attachments in rhesus monkeys: dogs as mother surrogates

Rhesus infants raised from birth with their mothers, age-mates, or cloth surrogates for periods varying fronm 1 to 10 months were separated from these objects and placed with dogs. Contrary to previous suggestions that were consistent with the notions of a critical period for attachment formation and irreversibility of filial bonds, the monkeys formed strong and specific attachments to their canine surrogates.     

Induction and suppression of RNA silencing by an animal virus

RNA silencing is a sequence-specific RNA degradation mechanism that is operational in plants and animals. Here, we show that flock house virus (FHV) is both an initiator and a target of RNA silencing in Drosophila host cells and that FHV infection requires suppression of RNA silencing by an FHV-encoded protein, B2. These findings establish RNA silencing as an adaptive antiviral defense in animal cells. B2 also inhibits RNA silencing in transgenic plants, providing evidence for a conserved RNA silencing pathway in the plant and animal kingdoms.     

Vernalization-mediated epigenetic silencing by a long intronic noncoding RNA

Vernalization is an environmentally-induced epigenetic switch in which winter cold triggers epigenetic silencing of floral repressors and thus provides competence to flower in spring. In Arabidopsis, winter cold triggers enrichment of tri-methylated histone H3 Lys(27) at chromatin of the floral repressor, FLOWERING LOCUS C (FLC), and results in epigenetically stable repression of FLC. This epigenetic change is mediated by an evolutionarily conserved repressive complex, polycomb repressive complex 2 (PRC2). Here, we show that a long intronic noncoding RNA [termed COLD ASSISTED INTRONIC NONCODING RNA (COLDAIR)] is required for the vernalization-mediated epigenetic repression of FLC. COLDAIR physically associates with a component of PRC2 and targets PRC2 to FLC. Our results show that COLDAIR is required for establishing stable repressive chromatin at FLC through its interaction with PRC2.     

APOBEC-mediated editing of viral RNA

Retroviral DNA can be subjected to cytosine-to-uracil editing through the action of members of the APOBEC family of cytidine deaminases. Here we demonstrate that APOBEC-mediated cytidine deamination of human immunodeficiency virus (HIV) virion RNA can also occur. We speculate that the natural substrates of the APOBEC enzymes may extend to RNA viruses that do not replicate through DNA intermediates. Thus, cytosine-to-uracil editing may contribute to the sequence diversification of many viruses.     

miRNA-mediated gene silencing by translational repression followed by mRNA deadenylation and decay

microRNAs (miRNAs) regulate gene expression through translational repression and/or messenger RNA (mRNA) deadenylation and decay. Because translation, deadenylation, and decay are closely linked processes, it is important to establish their ordering and thus to define the molecular mechanism of silencing. We have investigated the kinetics of these events in miRNA-mediated gene silencing by using a Drosophila S2 cell-based controllable expression system and show that mRNAs with both natural and engineered 3' untranslated regions with miRNA target sites are first subject to translational inhibition, followed by effects on deadenylation and decay. We next used a natural translational elongation stall to show that miRNA-mediated silencing inhibits translation at an early step, potentially translation initiation.     

植物病毒编码RNA沉默抑制子的研究进展

RNA沉默是真核生物用来抵抗病毒入侵的一种普遍而又古老的防御机制，而病毒在进化过程中也相应地产生了一些与之抗衡的功能，其中编码沉默抑制子就是对抗RNA沉默的有效策略。它们分别能够在不同阶段，以不同的方式干扰来自于寄主的RNA沉默，从而有效地建立侵染。本文主要针对目前已经发现的由植物病毒编码RNA沉默抑制子的作用特征、鉴定方法以及作用副效应进行综述，并讨论了RNA沉默抑制子的研究及应用前景。     

细粒棘球绦虫miRNAs的鉴定及分析

细粒棘球绦虫具有复杂的基因调控模式,在中间宿主和终末宿主体内具有截然不同的生物学特性。miRNA是真核生物内存在的非常重要的调控因子,本研究采用Solexa高通量测序技术,对G1株原头蚴mi-croRNAs进行了鉴定和分析,总共发现了108条miRNAs,其中26条属于保守家族,82条是细粒棘球绦虫特有。     

利用双荧光素酶报告系统鉴定靶向作用猪CD163基因的miRNA

为了进一步筛选获得抑制猪繁殖与呼吸综合征病毒(PRRSV)增殖的候选mi RNA,为猪繁殖与呼吸综合征(PRRS)防治及猪的抗病育种提供新策略,通过3′RACE(Rapid-amplification of c DNA ends)测序获得了猪CD163基因3′UTR的完整序列,生物信息学分析发现其具有mi R-181c、mi R-181d、mi R-23b、mi R-4262等mi RNA的作用靶点。利用双荧光素酶报告系统检测发现,与阴性对照组相比,mi R-181c、mi R-181d、mi R-23b和mi R-4262均可极显著(P0.01)抑制荧光素酶的相对活性,其中mi R-181d抑制效果最佳。     

基因编辑新技术研究进展

基因编辑是一项旨在对基因组进行定点修饰的新技术,目前主要有人工核酸酶介导的锌指核酸酶(ZFN)技术、转录激活子样效应物核酸酶(TALEN)技术和RNA引导的CRISPR-Cas核酸酶(CRISPR-Cas RGNs)技术。它们都能特异性地识别靶位点,对其单链或双链进行精准切割后,由细胞内源性的修复机制来完成对靶标基因的敲除和替换。本文比较了这3种基因编辑技术,并对其应用进展做了介绍。     

不明原因复发性自然流产胚胎绒毛组织MiRNAs的表达研究

利用miRCURY LNATM microRNA Arrays 10.0对不明原因复发性自然流产胚胎绒毛和正常胚胎绒毛组织miRNAs进行了检测.结果显示流产绒毛和正常绒毛组织有43个miRNAs存在明显表达差异(ratios≥2.O或ratios≤0.5).其中上调表达33个,下调表达10个.文献检索显示有12个差异表达miRNAs(上调10个,下调2个)已有功能研究报道,主要与细胞侵袭、离子转运和信号转导相关,另外31个尚无功能研究报道.该研究结果提示自然流产绒毛组织中某些差异表达的miRNAs可能与不明原因复发性自然流产的发生有关.