microRNAs (miRNAs) represent a class of noncoding RNA species, believed to be regulating gene expression by binding to complementary sites in the 3'UTRs of target mRNAs. They play important regulatory roles in various metabolic pathways in most eukaryotes. The recent discovery of virus encoded miRNAs suggests that viruses may be using them to regulate host and viral gene expression. Another class of closely related small interfering RNAs (siRNAs) also has been found within the HIV-1 genome and shown to be exerting a limited impact on virus reproduction. Additionally, an additional type of viral noncoding RNAs named small noncoding RNAs (sncRNAs) ranging from a few tens to a few hundred nucleotides in length, has also been identified. sncRNAs have a wide phylogenesis and high levels of expression, suggesting they may play an important roles in different species. Here we discuss the genomic organization, expression, conservation as well as potential function of virally encoded miRNA, siRNA, and sncRNAs.

中文翻译：

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病毒编码的microRNA，siRNA和其他小的非编码RNA的特性和功能。

microRNA（miRNA）代表一类非编码RNA，据信通过与靶mRNA的3'UTR中的互补位点结合来调节基因表达。它们在大多数真核生物的各种代谢途径中起重要的调节作用。病毒编码的miRNA的最新发现表明，病毒可能正在使用它们来调节宿主和病毒基因的表达。在HIV-1基因组中也发现了另一类密切相关的小干扰RNA（siRNA），显示它们对病毒繁殖的作用有限。另外，还鉴定了另一种类型的病毒非编码RNA，称为小非编码RNA（sncRNA），其长度范围从几十个核苷酸到几百个核苷酸。sncRNA具有广泛的系统发育和高水平的表达，表明它们可能在不同物种中起重要作用。在这里，我们讨论病毒编码的miRNA，siRNA和sncRNA的基因组组织，表达，保守性以及潜在功能。