Catalanotto Caterina, Cogoni Carlo, Zardo Giuseppe
Department of Cellular Biotechnologies and Hematology, University of Rome Sapienza, Rome 00179, Italy.
Int J Mol Sci. 2016 Oct 13;17(10):1712. doi: 10.3390/ijms17101712.
The finding that small non-coding RNAs (ncRNAs) are able to control gene expression in a sequence specific manner has had a massive impact on biology. Recent improvements in high throughput sequencing and computational prediction methods have allowed the discovery and classification of several types of ncRNAs. Based on their precursor structures, biogenesis pathways and modes of action, ncRNAs are classified as small interfering RNAs (siRNAs), microRNAs (miRNAs), PIWI-interacting RNAs (piRNAs), endogenous small interfering RNAs (endo-siRNAs or esiRNAs), promoter associate RNAs (pRNAs), small nucleolar RNAs (snoRNAs) and sno-derived RNAs. Among these, miRNAs appear as important cytoplasmic regulators of gene expression. miRNAs act as post-transcriptional regulators of their messenger RNA (mRNA) targets via mRNA degradation and/or translational repression. However, it is becoming evident that miRNAs also have specific nuclear functions. Among these, the most studied and debated activity is the miRNA-guided transcriptional control of gene expression. Although available data detail quite precisely the effectors of this activity, the mechanisms by which miRNAs identify their gene targets to control transcription are still a matter of debate. Here, we focus on nuclear functions of miRNAs and on alternative mechanisms of target recognition, at the promoter lavel, by miRNAs in carrying out transcriptional gene silencing.
小非编码RNA（ncRNA）能够以序列特异性方式控制基因表达这一发现对生物学产生了巨大影响。高通量测序和计算预测方法的最新进展使得几种类型的ncRNA得以发现和分类。基于其前体结构、生物合成途径和作用模式，ncRNA被分类为小干扰RNA（siRNA）、微小RNA（miRNA）、PIWI相互作用RNA（piRNA）、内源性小干扰RNA（endo-siRNA或esiRNA）、启动子相关RNA（pRNA）、小核仁RNA（snoRNA）和sno衍生RNA。其中，miRNA作为基因表达的重要细胞质调节因子出现。miRNA通过mRNA降解和/或翻译抑制作用作为其信使RNA（mRNA）靶标的转录后调节因子。然而，越来越明显的是，miRNA也具有特定的核功能。其中，研究最多且争议最大的活性是miRNA引导的基因表达转录控制。尽管现有数据相当精确地详细说明了这种活性的效应器，但miRNA识别其基因靶标以控制转录的机制仍存在争议。在这里，我们关注miRNA的核功能以及miRNA在启动子水平上通过替代机制识别靶标以进行转录基因沉默的情况。
