MicroRNAs (miRNAs) are a recently discovered family of endogenous, noncoding RNA molecules approximately 22 nt in length. miRNAs modulate gene expression post-transcriptionally by binding to complementary sequences in the coding or 3' untranslated region of target messenger RNAs (mRNAs). It is now clear that the biogenesis and function of miRNAs are related to the molecular mechanisms of various clinical diseases, and that they can potentially regulate every aspect of cellular activity, including differentiation and development, metabolism, proliferation, apoptotic cell death, viral infection and tumorgenesis. Here, we review recent advances in miRNA research, and discuss the diverse roles of miRNAs in disease.

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The discovery of large numbers of long non-coding RNAs (lncRNAs) has been driven by genome-wide transcriptional analyses. Compared to small ncRNAs, lncRNAs have been shown to harbor biological activities, but the functions of the great majority of lncRNAs are not known. There is growing evidence that lncRNAs can regulate gene expression at epigenetic, transcription, and post-transcription levels and widely take part in various physiological and pathological processes, such as participating in cell development, immunity, oncogenesis, clinical disease processes, etc. Here, the current research efforts on the function of lncRNA in recent years were summarized.

BackgroundNatural Killer (NK) cells are a crucial component of the host innate immune system with anti-viral and anti-cancer properties. However, the role of NK cells in West Nile virus (WNV) infection is controversial, with reported effects ranging from active suppression of virus to no effect at all. It was previously shown that K562-mb15-41BBL (K562D2) cells, which express IL-15 and 4-1BBL on the K562 cell surface, were able to expand and activate human primary NK cells of normal peripheral blood mononuclear cells (PBMC). The expanded NK cells were tested for their ability to inhibit WNV infection in vitro.ResultsCo-culture of PBMC with irradiated K562D2 cells expanded the NK cell number by 2-3 logs in 2-3 weeks, with more than 90% purity; upregulated NK cell surface activation receptors; downregulated inhibitory receptors; and boosted interferon gamma (IFN-γ) production by ~33 fold. The expanded NK (D2NK) cell has strong natural killing activity against both K562 and Vero cells, and killed the WNV infected Vero cells through antibody-dependent cellular cytotoxicity (ADCC). The D2NK cell culture supernatants inhibited both WNV replication and WNV induced cytopathic effect (CPE) in Vero cells when added before or after infection. Anti-IFN-γ neutralizing antibody blocked the NK supernatant-mediated anti-WNV effect, demonstrating a noncytolytic activity mediated through IFN-γ.ConclusionsCo-culture of PBMC with K562D2 stimulatory cells is an efficient technique to prepare large quantities of pure and active NK cells, and these expanded NK cells inhibited WNV infection of Vero cells through both cytolytic and noncytolytic activities, which may imply a potential role of NK cells in combating WNV infection.

Host factors interacting with the dengue virus (DENV) 39 UTR are involved in virus replication, but their roles remain poorly understood. We used RNA affinity capture and mass spectrometry to identify p100 as a host cellular protein associated with the DENV 39 UTR. By using RNA immunoprecipitation and confocal immunofluorescence analysis we demonstrated an interaction between p100 and the 39 UTR in DENV-infected cells. We identified the A4 region (the extensive stem-loop structure at the 39 end) as the binding site of p100 by studying deletion mutants. p100 knockdown specifically reduced the levels of viral RNA and viral protein in DENV-infected cells. Furthermore, downregulation of p100 reduced the expression of a heterologously expressed luciferase-39 UTR(DENV) mRNA in an A4-dependent manner, confirming the binding data and the effects of p100 knockdown on viral replication. These results provide evidence that p100 interacts with the 39 UTR of DENV and is required for normal DENV replication.

microRNAs (miRNAs) are 20-24 nucleotide (nt) RNAs that regulate eukaryotic gene expression post-transcriptionally by the degradation or translational inhibition of their target messenger RNAs (mRNAs). To identify miRNA target genes will help a lot by understanding their biological functions. Sophisticated computational approaches for miRNA target prediction, and effective biological techniques for validating these targets now play a central role in elucidating their functions. Owing to the imperfect complementarity of animal miRNAs with their targets, it is difficult to judge the accuracy of the prediction. Complexity of regulation by miRNA-mediated targets at protein and mRNAs levels has made it more challenging to identify the targets. To date, only a few miRNAs targets are confirmed. In this article, we review the methods of miRNA target prediction and the experimental validation for their corresponding mRNA targets in animals.

Brucella spp. infection results in compromised Type1 (Th1) cellular immune response. Several reports have described an immunomodulatory function for Brucella major outer membrane protein Omp25. However, the mechanism by which Omp25 modulates macrophage dysfunction has not been defined. Herein, we reported that Omp25-deficient mutant of Brucella suis exhibited an enhanced ability to induce interleukin (IL)-12 whereas ectopic expression of Omp25 protein inhibited TLR agonists-induced IL-12 p70 production through suppression of both IL-12 p40 and p35 subunit expression in THP-1 cells. In addition, Omp25 significantly upregulated miR-155, -23b and -21-5p, as well as the immunomodulator molecule programmed death-1 (PD-1) in monocyte/macrophages. The upregulation of miR-155 and -23b correlated temporally with decreased TAB2 levels, IκB phosphorylation and IL-12 p40 levels by targeting TAB2 and il12B 3′ untranslated region (UTR), respectively, while miR-21-5p increase directly led to the reduction of lipopolysaccharide (LPS)/R848-induced IL-12 p35 protein by targeting il12A 3′UTR. Consistent with this finding, reduction of miR-155 and -23b attenuated the inhibitory effects of Omp25 on LPS/R848-induced IL-12 p40 expression at both transcriptional and posttranscriptional levels, while reduction of miR-21-5p attenuated the inhibitory effects of Omp25 on LPS/R848-induced IL-12 p35 expression at the posttranscriptional level, together significantly enhanced IL-12 p70 production upon LPS/R848 stimulation. We also found that blocking PD-1 signaling decreased the expression of miR-155, -23b and -21-5p induced by Omp25 and enhanced IL-12 production in monocyte/macrophages. Altogether, these data demonstrate that Brucella Omp25 induces miR-155, -23b and -21-5p to negatively regulate IL-12 production at both transcriptional and posttranscriptional levels via regulation of PD-1 signaling, which provides an entirely new mechanism underlying monocyte/macrophages dysfunction during Brucella spp. infection.

Recently, using large-scale genomic sequencing, a great number of small noncoding RNAs (ncRNA) has been discovered. Short ncRNAs can be classified into three major classes--small interfering RNA (siRNA), microRNA (miRNA), and piwi-interacting RNA (piRNA). These short ncRNAs ranging from 20 to 300 nt in size are now recognized as a new paradigm of gene regulation for controlling many biological processes. In this paper, we review the biogenesis and recent research on the functions of small regulatory non-coding RNAs and aim at understanding their important functions in living organisms.