Cellular microRNA let‐7c inhibits M1 protein expression of the H1N1 influenza A virus in infected human lung epithelial cells

Abstract

The influenza virus (IV) triggers a series of signalling events inside host cells and induces complex cellular responses. Studies have suggested that host factors play an essential role in IV replication. MicroRNAs (miRNAs) represent a class of small non-coding RNAs that target mRNAs, triggering either translation repression or RNA degradation. Emerging research suggests that host-derived cellular miRNAs are involved in mediating the host–IV interaction. Using miRNA microarrays, we identified several miRNAs aberrantly expressed in IV-infected human lung epithelial cells (A549). Specifically, miR-let-7c was highly up-regulated in IV-infected A549 cells. PITA and miRanda database screening indicated that the let-7c seed sequence is a perfect complementary sequence match to the 3′ untranslated region (UTR) of viral gene M1 (+) cRNA, but not to PB2 and PA. As detected by a luciferase reporter system, let-7c directly targeted the 3′-UTR of M1 (+) cRNA, but not PB2 and PA. To experimentally identify the function of cellular let-7c, precursor let-7c was transfected into A549 cells. Let-7c down-regulated IV M1 expression at both the (+) cRNA and protein levels. Furthermore, transfection with a let-7c inhibitor enhanced the expression of M1. Therefore, let-7c may reduce IV replication by degrading M1 (+) cRNA. This is the first report indicating that cellular miRNA regulates IV replication through the degradation of viral gene (+) cRNA by matching the 3′-UTR of the viral cRNA. These findings suggest that let-7c plays a role in protecting host cells from the virus in addition to its known cellular functions.

Replication of Many Human Viruses Is Refractory to Inhibition by Endogenous Cellular MicroRNAs

“…Moreover, it has also been suggested that endogenous cellular miRNAs can exert a significant antiviral effect on wild-type viruses in human cells (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), and it is certainly true that mutant viruses engineered to contain target sites for a specific cellular miRNA are severely attenuated in their ability to grow in cells that express that miRNA (74)(75)(76)(77)(78).…”

“…Over a thousand distinct miRNAs are encoded within the human and mouse genomes, and these are frequently expressed in a highly tissue-specific manner (5,19). Therefore, any virus growing in a mammalian cell will transcribe mRNAs that have the potential to be inhibited by endogenous cellular miRNAs, and there have indeed been a number of studies reporting the inhibition of human immunodeficiency virus type 1 (HIV-1), influenza A virus (IAV), enterovirus, vesicular stomatitis virus (VSV), and primate foamy virus mRNAs, among others, by cellular miRNAs (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30). However, miRNAs are highly conserved during evolution, and as targeting of an mRNA by an miRNA can potentially be blocked by single-nucleotide changes in the RNA target, it seems probable that viruses would have evolved to be largely refractory to inhibition by endogenous miRNAs (31).…”

“…Given the potential importance of RNAi in limiting viral replication and especially given recent reports arguing that both siRNAs and endogenous miRNAs can inhibit virus replication in mammalian somatic cells (17,18,(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), we decided to rigorously test whether viruses are indeed either dependent on, or restricted by, siRNAs or endogenous miRNAs expressed in human cells. For this purpose, we used genome editing to generate human cell lines that entirely lack Dicer function and that therefore are unable to generate endogenous miRNAs or siRNAs (41), and we analyzed the abilities of a wide range of human viruses to replicate in these cells in culture.…”

MicroRNA-33a disturbs influenza A virus replication by targeting ARCN1 and inhibiting viral ribonucleoprotein activity

“…To regulate virus replication, miRNA may target three types of genes: genes involved in the antiviral immune response, host genes required for the virus life cycle or viral genes (Izzard et al, 2014;Ma et al, 2012;Rosenberger et al, 2012;Song et al, 2010;Zhang et al, 2014). We found that miRNA-33a exerts its inhibitory effect by repressing the expression of ARCN1, a host factor that is crucial for influenza virus replication.…”

Insights into RNA Interference as Antiviral Defense

“…The group of human miRNAs including miR-28, miR-125b, miR-150, miR-223 and miR-382 targets 3' end of HIV-1 mRNAs and significantly decrease HIV-1 replication in n resting CD4 + T cells [40]. Similarly, mir-let-7c, mir-192 and mir-142 inhibit influenza virus replication [41][42][43].…”