COVID-19 researchGene: DICER1
Evidence Summary from Illumina curation team (Alison Coffey and Julie Taylor): The DICER1 gene, located on chromosome 14, position q32.13, was discovered in 2001 by Bernstein and is a member of the RNase III family, (also known as dicer 1, ribonuclease III; dicer1, Dcr-1 homolog (Drosophila); multinodular goitre 1). DICER1 is involved in the generation of double-stranded microRNAs (miRNAs), short non-coding RNAs, the cleavage of dsRNA into siRNAs, along with the biogenesis of numerous other small RNAs. There is increasing evidence DICER1 is also involved in regulating many other essential cellular processes such as those related to chromatin remodeling, inflammation, apoptosis and cell survival (Kurzynska-Kokorniak et al. 2015; Song and Rossi, 2017). DICER1 encodes a ∼220-KDa protein (RNase III endoribonuclease) which is a crucial component of the RNA Induced Silencing Complex (RISC) loading complex (RLC), comprised of dicer, Argonaute-2 (AGO-2), and trans-activation-responsive RNA binding protein 2 (TARBP2). The encoded protein is required by the RNA interference (RNAi) and small temporal RNA (stRNA) pathways to produce the active small RNA component which has a role in modulating gene expression at the post-transcriptional level. Research has shown that expression levels of cellular transcript and protein dicer are strictly controlled, with aberrant regulation contributing to carcinogenesis, neurodegenerative, rheumatic and immune system disorders. Studies have concluded that the encoded dicer ribonuclease-dependent processing of dsRNA viral replication intermediates into successive siRNAs is a conserved mammalian immune response to infection by positive-strand RNA viruses (Svobodova et al. 2016 summary & fig1; Li et al. 2013; Ding et al. 2018). Moreover, miRNAs play an important role in host-virus interactions in mammals (See Maillard et al. 2019 REVIEW; Foulkes et al. 2014 REVIEW).
The cre-lox method for dicer1 gene knockout has been employed for studies into the role of dicer1 in immune cell development and function. Studies of dicer1 fl/fl mice have indicated short survival times along with severely impaired GMP differentiation into monocytes, neutrophils, myeloid DCs & mature macrophages. (Devasthanam et al. 2014). Results conclude that dicer1 is important in immune response and also vital for cell survival and apoptosis pathways. Muljo et al. (2005) investigated a conditional allele of dicer-1 (dcr-1) within a mouse model and showed that specific dcr-1 deletion in the T-cell lineage, resulted in impaired development of T-cells & aberrant cell differentiation of T-helper cells & cytokine production. Dcr-1 deletion in the thymus resulted in severe block in development of CD8+ T cells and resulted in defective microRNA processing in CD4+ T-cells. The results demonstrate Dicer regulates diverse aspects of T-cell biology along with cytokine production during T-cell differentiation where dicer-deficient T-cells preferentially express interferon-ƴ.
Research by Galiana-Arnoux et al. (2006), of DICER in drosophila (drosophila have two dicer genes) have identified that DICER genes (Dcr1, miRNA pathway and Dcr2, RNAi pathway) control production of siRNA and a loss-of-function mutation in Dcr2 resulted in increased susceptibility to three different families of RNA viruses. Qi et al. (2012) research into RNAi gene silencing mechanism show that the B2 protein in Wuhan nodavirus (WhNV) suppresses Dcr2 in drosophila by direct interaction with the PAZ and RNAse III domains therefore blocking processing of dsRNA and siRNA. Evidence of a dicer antiviral system was also reported by Machitani et al. (2016) for mammalian human adenoviruses where DICER1 gene knockdown increased the copy number of adenovirus-encoding small RNAs (VA-RNAs) leading to the promotion of adenovirus replication; conversely, dicer overexpression significantly inhibited viral replication.
Modai et al. (2019) conclude that HIV-1 infection inhibits DICER1 by altering miRNA expression. They conclude that upon HIV-1 infection, human miR-186, 210 and 222 directly regulate DICER1 gene expression causing down-regulation of the gene contributing to impaired cell-mediated immunity (fig6). Other methods of inhibition are from viral proteins, termed viral suppressors of RNA silencing, which interact and inhibit dicer ribonuclease activity in HIV-1 and hepatitis C infections. These viral proteins may mediate proteasomal degradation of endoribonuclease dicer through CRL4DCAF1 ubiquitin ligase complex (Klockow et al. 2013), interact directly via the core protein (Chen et al. 2008) or HIV-1 transactivation of transcription (Bennasser and Jeang, 2006). Through these methods they can block dicer interactions with TRBP2 or ADAR1, boost macrophage infection, and subsequently reduce the function of short hairpin RNAs (shRNAs) which thus inhibit RNA silencing. Ultimately these viruses, though various methods, supress the ability of dicer to process dsRNAs into siRNAs boosting viral infection and pathogenesis.
Downregulation of DICER1 gene expression has additionally been found in cord blood of infants with severe respiratory syncytial virus (RSV), prior to RSV exposure, indicating this reduced expression may predispose newborns to RSV disease. Inchley et al. (2011) theorize that this occurs via disruption of leukocyte gene regulation of miRNA and direct anti-viral RNAi mechanisms. (Inchley et al. 2011 see section on “Dicer Gene Expression”).
Otsuka et al. (2007) have shown using gene-trap methods to obtain viable dicer1 fl/fl mice where dicer1 deficiency caused impairment of miR24 and miR93 production resulting in susceptibility to vesticular stomatitis virus (VSV) and herpes simplex-1 virus, but not other viruses tested.
SARS CoV & SARS CoV-2
Recently, Pasquier and Robichon, 2020 (preprint) have investigated the Dicer host immunity system regarding SARs-CoV-2 within a computational approach, concluding SARS-CoV2 may manipulate this system of immunity against its host, requiring further research. Mu et al., 2020 suggest SARs-CoV2 suppresses RNAi thus preventing recognition by the encoded ribonuclease dicer protein
Viral suppressors of RNA silencing (VSRs) suppress RNAi at pre or post-dicer level to overcome host defense and establish infection. Cui et al. (2015) from Wuhan University laboratory of virology, identified a novel VSR from coronaviruses (CoVs) including Severe acute respiratory syndrome coronavirus (SARS-CoV) and showed that the coronavirus nucelocaspid protein (N-protein), conserved and expressed in all coronaviruses, suppressed RNAi triggered by either short hairpin RNAs or small interfering RNAs in mammalian cells. They went on to show using mouse hepatitis virus A-59 (MHV-A59) which is closely linked to SARS-CoV in the family coronaviridae, that the viral replication was increased when the N proteins (novel VSR) were expressed but that knockdown of DICER1 gene or Ago2 transcripts facilitated the viral replication specifically in mammalian cells. They demonstrate that the N-protein of CoVs could efficiently inhibit dicer-mediated dsRNA cleavage and post-Dicer activities by sequestering dsRNAs and siRNAs. Kannan et al. (2020) performed clustal W analysis of N-Protein for SARS-CoV and COVID-19 demonstrating 90% sequence identity from an NCBI amino acid blast of both nucleocapsid (N) protein sequences (figure2). They suggest that the N-protein of COVID-19 may also function as a VSR for RNAi to overcome host defense. Ding et al. (2017) show that both MHV and SARS-CoV N proteins can also disrupt protein activator of protein kinase R (PACT), a cellular dsRNA-binding protein which binds to RIG-I and MDA5 to activate interferon (IFN) production to prevent antiviral host response.
PMID: 17181864: Bennasser and Jeang, 2006
• HIV-1 Tat Interaction With Dicer: Requirement for RNA
• Tat-Dicer interaction depends on RNA, requires the helicase domain of Dicer, and is independent of Tat's transactivation domain.
PMID: 18325616: Chen et al., 2008
• HCV Core Protein Interacts With Dicer to Antagonize RNA Silencing
PMID: 26085159: Cui et al., 2015
• The Nucleocapsid Protein of Coronaviruses Acts as a Viral Suppressor of RNA Silencing in Mammalian Cells
PMID: 24303839: Devasthanam et al, 2014
• This study investigates the role of the dicer protein in immune cell development and function using dicer1 cre-lox knockout models to conditionally ablate dicer1 in different immune cell subsets.
PMID: 28591694: Ding et al., 2017
• The nucleocapsid proteins of mouse hepatitis virus and severe acute respiratory syndrome coronavirus share the same IFN-β antagonizing mechanism: attenuation of PACT-mediated RIG-I/MDA5 activation
PMID: 30015086: Ding et al., 2018
• Antiviral RNA Interference in Mammals: Indicates infection of plants and insects with RNA and DNA viruses triggers Dicer-dependent production of virus-derived small interfering RNAs (vsiRNAs), which subsequently guide specific virus clearance by RNA interference (RNAi).
PMID: 25176334: Foulkes et al., 2012-REVIEW
• Review of DICER1: DICER1 Mutations, microRNAs and Mechanisms
PMID: 16554838: Galiana-Arnoux et al., 2006
• Essential function in vivo for Dicer-2 in host defense against RNA viruses in drosophila.
• https://pubmed.ncbi.nlm.nih.gov/16554838/ or https://www.nature.com/articles/ni1335
PMID: 21385408: Inchley et al., 2011
• Investigates ribonuclease Dicer and analyzed the gene expression of Dicer in newborns of which 37 infants had sufficient cord blood RNA with confirmed RSV disease <1yr. Demonstrates significant reduced Dicer expression in cord blood prior to severe disease in infants <1yr later. Conclude downregulation may predispose infants to RSV disease.
PMID: 32141569: Kannan et al., 2020
• COVID-19 (Novel Coronavirus 2019) - Recent Trends
• Perform W cluster analysis of COVID-19 and SARS-CoV nucleocapsid (N) protein sequences of the viruses showing 90% amino acid sequence similarity. Suggest the N-protein may be a VSR in RNAi by targeting DICER.
PMID: 23849790: Klockow et al., 2013
• The HIV-1 Protein Vpr Targets the Endoribonuclease Dicer for Proteasomal Degradation to Boost Macrophage Infection
PMID: 25883138: Kurzynska-Kokorniak et al., 2015
• Investigating the complexity of the mechanisms regulating Dicer gene expression and enzyme activities
PMID: 24115437: Li et al, 2013
• Investigates RNA interference pathways in antiviral immunity in mammals overviewing dicer processing of dsRNA viral replication intermediates into siRNAs.
PMID: 27273616: Machitani et al., 2016
• Dicer functions as an antiviral system against human adenoviruses via cleavage of adenovirus-encoded noncoding RNA
PMID: 30872283: Maillard et al., 2019- REVIEW
• Reviewing DICER1 within the anti-viral RNAi pathway in mammals
PMID: 30682089: Modai et al, 2019
• HIV-1 infection increases miRNAs which inhibit Dicer
PMID: 32291557: Mu et al, 2020
• SARS-CoV-2-encoded nucleocapsid protein acts as a viral suppressor of RNA interference in cells
PMID: 16009718: Muljo et al., 2005
• Indicates absence of dicer results in abberant T-cell differentiation.
PMID: 17613256: Otsuka, et al 2007
• Hypersusceptibility to Vesicular Stomatitis Virus Infection in Dicer1-Deficient Mice Is Due to Impaired miR24 and miR93 Expression
No PMID: Preprint : Pasquier and Rubichon, 2020
• SARS-CoV-2 might manipulate against its host the immunity RNAi/Dicer/Ago system
PMID: 22438534: Qi et al., 2012
• Targeting of Dicer-2 and RNA by a Viral RNA Silencing Suppressor in Drosophila Cells
PMID: 28473628: Song and Rossi, 2017
• Molecular Mechanisms of Dicer: Endonuclease and Enzymatic Activity
Created: 28 May 2020, 3:16 p.m. | Last Modified: 28 May 2020, 3:18 p.m.
Panel Version: 0.348
Identified through an OMIM search for potential viral susceptibility genes, and subsequently triaged/reviewed by Illumina curation team.
Created: 28 May 2020, 12:36 p.m. | Last Modified: 28 May 2020, 12:36 p.m.
Panel Version: 0.336
gene: DICER1 was added gene: DICER1 was added to COVID-19 research. Sources: Expert list,OMIM,Expert Review Green Mode of inheritance for gene: DICER1 was set to Unknown