MicroRNA let-7f-5p Inhibits Porcine Reproductive and Respiratory Syndrome Virus by Targeting MYH9

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important viral pathogens in the swine industry. Current antiviral strategies do not effectively prevent and control PRRSV. Recent reports show that microRNAs (miRNAs) play vital roles in viral infections by post transcriptionally regulating the expression of viral or host genes. Our previous research showed that non-muscle myosin heavy chain 9 (MYH9) is an essential factor for PRRSV infection. Using bioinformatic prediction and experimental verification, we demonstrate that MYH9 expression is regulated by the miRNA let-7f-5p, which binds to the MYH9 mRNA 3′UTR and may play an important role during PRRSV infection. To understand how let-7f-5p regulates PRRSV infection, we analyzed the expression pattern of both let-7f-5p and MYH9 in porcine alveolar macrophages (PAMs) after infection with either highly pathogenic PRRSV (HP-PRRSV) or classical type PRRSV (N-PRRSV) using a deep sequencing approach with quantitative real-time PCR validation. Our results showed that both HP-PRRSV and N-PRRSV infection reduced let-7f-5p expression while also inducing MYH9 expression. Furthermore, let-7f-5p significantly inhibited PRRSV replication through suppression of MYH9 expression. These findings not only provide new insights into the pathogenesis of PRRSV, but also suggest potential new antiviral strategies against PRRSV infection.

Cellular microRNA miR-c89 inhibits replication of porcine reproductive and respiratory syndrome virus by targeting the host factor porcine retinoid X receptor β

“…Similar to the results of this study, our previous study found that miR-10a-5p could suppress PRRSV replication by inhibiting host SRP14 expression [25]. miRNA let-7f-5p significantly inhibits PRRSV replication by inhibiting MYH9 expression [26]. These miRNAs can modulate host factors in response to antiviral responses of the body after PRRSV infection.…”

“…Quantitative PCR (qPCR) was performed using the Step One Plus Real-Time PCR System (Applied Biosystems) and FastStart Universal SYBR Green Master Mix (Roche) with RXRB-specific forward and reverse primers (5′-GTGA AGCC ACCA GTCT TAGGG-3′ and 5′-AGTA GGTC AGGT CCTT ACGGATG-3, respectively) and PRRSV ORF7-specific forward and reverse primers (5′-AGATCATCGCCCAACAAAAC-3′ and 5′-GACACAATTGCCGCTCACTA-3′, respectively) being used as described previously [37]. HPRT1 mRNA was used as an internal standard for quantification, and HPRT1specific forward and reverse primers (5′-TGGA AAGA ATGT CTTG ATTG TTGAAG-3′ and 5′-ATCT TTGG ATTA TGCT GCTTGACC-3′, respectively) were used for detection [26].…”

Molecular and Cellular Mechanisms for PRRSV Pathogenesis and Host Response to Infection

“…HP-PRRSV nsp4 has greater inhibitory effect on IFNβ than nsp4 of less pathogenic strains. As discussed above, nsp1α binds to and degrades SLA-I (Du et al, 2016a), A recent study supports this finding that HP-PRRSV nsp4 also downregulates the cellular level of β2microglobulin (β2M) (Qi et al, 2017), which forms a heterotrimeric complex with the SLA-I heavy chain and plays a critica1 role in SLA-I antigen presentation. PRRSV nsp4 binds to the B2M promoter and suppresses β2M transcription.…”

“…Interestingly, nsp1α binds to swine leukocyte antigen class I (SLA-I) and mediates the SLA-I degradation in a ubiquitin-proteasome-dependent manner (Du et al, 2016a). It is thus tempting to speculate that nsp1α may have an ubiquitin E3 ligase activity.…”

“…Overexpression of HO-1 inhibits PRRSV replication, and in turn, PRRSV downregulates the HO-1 expression (Xiao et al, 2015). The HO-1 mRNA and miR-24-3p interact directly, which significantly decreases the HO-1 protein production (N. Li et al, 2016a). PRRSV infection induces miR-24-3p expression, and collectively, miR-24-3p promotes PRRSV replication through suppression of HO-1 expression, suggesting a potential as an antiviral drug against PRRSV infection.…”