LncRNA MIAT enhances systemic lupus erythematosus by upregulating CFHR5 expression via miR-222 degradation.

Systemic lupus erythematosus (SLE), a complex polygenic autoimmune disease, is associated with increased complement activation. Complement factor H related protein 5 (CFHR5) may contribute to dysfunctional complement activation, thus predisposing to SLE. The expression levels of anti-dsDNA, C3 and CFHR5 in blood samples from 50 SLE patients and 50 healthy individuals were evaluated, and also their expression levels were measured in an MRL/lpr mouse model and control MRL/MPJ mice. The results showed that CFHR5 expression increased in SLE patients together with the increase of anti-dsDNA in comparison with the healthy control. Furthermore, CFHR5 expression was inversely correlated with C3, down-regulation of which was associated with worse SLE. Previous studies indicated that long noncoding RNA (lncRNA) regulates mRNA synthesis via microRNA (miRNA) inhibition. The present bioinformatics analysis revealed that the target miRNA (miR-222) was combined with both lncRNA MIAT and mRNA CFHR5. H&E staining of the kidney tissues of the MRL/lpr mice revealed that lncRNA MIAT, as a competitive inhibitor of miR-222, enhanced SLE by upregulating CFHR5 expression through the degradation of miR-222 in vivo. Thus, our study revealed for the first time the role of lncRNA MIAT in regulating CFHR5 expression in SLE in vivo and provided new insights into the role of lncRNA in regulation and complement function of SLE pathogenesis.

Human cytomegalovirus miR-UL36-5p inhibits apoptosis via downregulation of adenine nucleotide translocator 3 in cultured cells.

Human cytomegalovirus (HCMV) encodes at least 26 microRNAs (miRNA). These miRNAs are utilized by HCMV to regulate its own genes as well as the genes of the host cell during infection. It has been reported that a cellular gene, solute carrier family 25, member 6 (SLC25A6), which is also designated adenine nucleotide translocator 3 (ANT3), was identified as a candidate target of hcmv-miR-UL36-5p by hybrid PCR. In this study, ANT3 was further demonstrated to be a direct target of hcmv-miR-UL36-5p by luciferase reporter assays. The expression level of ANT3 protein was confirmed, by western blotting, to be directly downregulated by overexpression of hcmv-miR-UL36-5p in HEK293 cells, U373 cells and HELF cells. Moreover, HCMV-infected cells showed a decrease in the ANT3 protein level. Using ANT3-specific small interfering RNA (siRNA) and an inhibitor for hcmv-miR-UL36-5p, it was shown that inhibition of apoptosis by hcmv-miR-UL36-5p in these cells specifically occurred via inhibition of ANT3 expression. These results imply that hcmv-miR-UL36-5 may play the same role during actual HCMV infection in order to establish a balance between the host cell and the virus.

Human cytomegalovirus miR-US4-5p promotes apoptosis via downregulation of p21-activated kinase 2 in cultured cells.

The human cytomegalovirus (HCMV) encodes ≥26 microRNAs (miRNAs). These miRNAs are utilized by HCMV to regulate its own genes in addition to the genes of the host cell, during infection. The present study first identified p21­activated kinase 2 (PAK2) as a target of hcmv­miR­US4­5p, via hybrid polymerase chain reaction, which was further verified using a luciferase reporter assay. The protein expression level of PAK2, detected via western blotting, was demonstrated to be directly downregulated by overexpression of hcmv­miR­US4­5p in HEK293, HELF and THP­1 cells. Furthermore, it was demonstrated that the PAK2 protein level in naturally infected HELF cells was gradually decreased at 24, 48 and 72 h post infection with increased hcmv­miR­US4­5p expression. The use of PAK2­specific small interfering RNA and an inhibitor for hcmv­miR­US4­5p, demonstrated that the promotion of apoptosis by hcmv­miR­US4­5p in these cells was specifically mediated via inhibition of PAK2 expression. These results indicated that hcmv­miR­US4­5p may exhibit this activity during natural HCMV infection, in order to establish a balance between the host cell and virus.

Human cytomegalovirus miR-US5-1 inhibits viral replication by targeting Geminin mRNA.

Viruses commonly create favorable cellular conditions for their survival through multiple mechanisms. MicroRNAs (miRNAs), which function as post-transcriptional regulators, are utilized by human cytomegalovirus (HCMV) in its infection and pathogenesis. In the present study, the DNA replication inhibitor Geminin (GMNN) was identified to be a direct target of hcmv-miR-US5-1. Overexpression of hcmv-miR-US5-1 could block the accumulation of GMNN during HCMV infection, and the decrease of GMNN expression caused by hcmv-miR-US5-1 or GMNN specific siRNA reduced HCMV DNA copies in U373 cells. Meanwhile, ectopic expression of hcmv-miR-US5-1 and consequent lower expression of GMNN influenced host cell cycle and proliferation. These results imply that hcmv-miR-US5-1 may affect viral replication and host cellular environment by regulating expression kinetics of GMNN during HCMV infection.

Human cytomegalovirus-encoded miR-US4-1 promotes cell apoptosis and benefits discharge of infectious virus particles by targeting QARS.

Human cytomegalovirus (HCMV) can cause congenital diseases and opportunistic infections in immunocompromised individuals. Its functional proteins and microRNAs (miRNAs) facilitate efficient viral propagation by altering host cell behaviour. Identification of functional target genes of miRNAs is an important step in studies on HCMV pathogenesis. In this study, Glutaminyl-tRNA Synthetase (QARS), which could regulate signal transduction pathways for cellular apoptosis, was identified as a direct target of hcmv-miR-US4-1. Apoptosis assay revealed that as silence of QARS by ectopic expression of hcmv-miR-US4-1 and specific small interference RNA of QARS can promote cell apoptosis in HCMV-infected HELF cells. Moreover, viral growth curve assays showed that hcmv-miR-US4-1 benefits the discharge of infectious virus particles. However, silence of hcmv-miR-US4-1 by its specific inhibitor overturned these effects. These results imply that hcmv-miR-US4-1 might have the same effects during HCMV nature infection. In general, hcmv-miR-US4-1 may involve in promoting cell apoptosis and benefiting discharge of infectious virus particles via down-regulation of QARS in HCMV-infected HELF cells.

Human cytomegalovirus microRNA miR-US25-1-5p inhibits viral replication by targeting multiple cellular genes during infection.

MicroRNAs (miRNAs) play important roles in regulating various cellular processes in plants, animals, and viruses. This mechanism is also utilized by human cytomegalovirus (HCMV) in the process of infection and pathogenesis. The HCMV-encoded miRNA, hcmv-miR-US25-1-5p, was highly expressed during lytic and latent infections, and was found to inhibit viral replication. Identification of functional target genes of this microRNA is important in that it will enable a better understanding of the function of hcmv-miR-US25-1-5p during HCMV infection. In the present study, 35 putative cellular transcript targets of hcmv-miR-US25-1-5p were identified. Down-regulation of the targets YWHAE, UBB, NPM1, and HSP90AA1 by hcmv-miR-US25-1-5p was validated by luciferase reporter assay and Western blot analysis. In addition, we showed that hcmv-miR-US25-1-5p could inhibit viral replication by interacting with these targets, the existence of which may impact virus replication directly or indirectly.

Human cytomegalovirus miR-US33-5p inhibits viral DNA synthesis and viral replication by down-regulating expression of the host Syntaxin3.

During infection with human cytomegalovirus (HCMV), overexpression of hcmv-miR-US33 can inhibit the lytic viral replication and down-regulate US29 mRNA. However, it remains unknown whether inhibition of viral replication by miR-US33 is mediated by down-regulation of expression of US29 or another host gene. Here, we identified the host gene Syntaxin3 (STX3) to be a direct target of hcmv-miR-US33-5p using Hybrid-PCR and luciferase-reporter assays. It was further demonstrated that the levels of STX3 protein were down-regulated in hcmv-miR-US33-5p-overexpressing cells. Experiments with STX3-specific siRNA, or with an inhibitor of hcmv-miR-US33-5p confirmed that hcmv-miR-US33-5p-mediated inhibition of HCMV DNA synthesis and of viral replication are specifically mediated by down-regulation of STX3 expression.