Dual regulation of hepatitis C viral RNA by cellular RNAi requires partitioning of Ago2 to lipid droplets and P-bodies

Berezhna, Svitlana; Supeková, Lubica; Sever, Mary J.; Schultz, Peter G.; Deniz, Ashok A.

doi:10.1261/rna.2523911

Cited by 26 publications

(26 citation statements)

References 67 publications

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“…Because Argonaute depletion did not alter P-body abundance (Fig. 5E), we hypothesize that the Argonaute proteins regulate HIV-1 infectivity by a mechanism which is independent of these foci, perhaps similar to Ago2-mediated regulation of hepatitis C virus replication (9).…”

Section: Discussionmentioning

confidence: 88%

HIV-1 Replication and APOBEC3 Antiviral Activity Are Not Regulated by P Bodies

Phalora

Sherer

Wolinsky

et al. 2012

J Virol

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The APOBEC3 cytidine deaminases play a critical role in host-mediated defense against exogenous viruses, most notably, human immunodeficiency virus type-1 (HIV-1) and endogenous transposable elements. APOBEC3G and APOBEC3F interact with numerous proteins that regulate cellular RNA metabolism, including components of the RNA-induced silencing complex (RISC), and colocalize with a subset of these proteins to mRNA processing bodies (P bodies), which are sites of mRNA translational repression and decay. We sought to determine the role of P bodies and associated proteins in HIV-1 replication and APOBEC3 antiviral activity. While we established a positive correlation between APOBEC3 protein incorporation into virions and localization to P bodies, depletion of the P-body components DDX6 or Lsm1 did not affect HIV-1 replication, APOBEC3 packaging into virions or APOBEC3 protein mediated inhibition of HIV-1 infectivity. In addition, neither HIV-1 genomic RNA nor Gag colocalized with P-body proteins. However, simultaneous depletion of multiple Argonaute family members, the effector proteins of RISC, could modestly increase viral infectivity. Because some APOBEC3 proteins interact with several Argonaute proteins, we also tested whether they could modulate microRNA (miRNA) activity. We found no evidence for the specific regulation of miRNA function by the APOBEC3 proteins, though more general effects on transfected gene expression were observed. In sum, our results indicate that P bodies and certain associated proteins do not regulate HIV-1 replication or APOBEC3 protein antiviral activity. Localization to P bodies may therefore provide a means of sequestering APOBEC3 enzymatic activity away from cellular DNA or may be linked to as yet unidentified cellular functions.

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Section: Discussionmentioning

confidence: 88%

HIV-1 Replication and APOBEC3 Antiviral Activity Are Not Regulated by P Bodies

Phalora

Sherer

Wolinsky

et al. 2012

J Virol

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“…This phenomenon was unlike that observed during poliovirus infection, where the abundance of Xrn1, Dcp1a, and Pan3 decreased by 5 h postinfection, likely as a result of virus-induced proteolytic cleavage (8). Rather, confocal microscopy showed that HCV likely dispersed P-bodies by relocalizing a number of P-body components (Lsm1, RCK/p54, DDX3, Dcp2, Xrn1, Ago2, and miR-122) to lipid droplets, the proposed sites of HCV assembly (7,9,10). Biochemical isolation and immunoblotting of lipid droplets con-firmed the localization of RCK/p54 and DDX3 on lipid droplets (9).…”

Section: Processing Bodies (P-bodies) and Hcvmentioning

confidence: 70%

“…Cross-linking and immunoprecipitation studies demonstrated that Ago2 interacted with HCV RNA not only at the known miR-122 binding sites but also in the IRES, E1, E2, NS5A, and NS5B regions (15). Ago2 and miR-122 colocalization at lipid droplets (10), and the additional Ago2-HCV RNA interactions (15), pose interesting questions concerning whether Ago2 might act beyond the microRNA-directed function during HCV infection. Furthermore, in light of the recent study describing adaptive mutations in HCV impacting miR-122-independent gene expression, would Ago2 still be required for HCV gene expression?…”

Section: P-body Components Affect Hcv Gene Expressionmentioning

confidence: 99%

Hepatitis C Virus Exploitation of Processing Bodies

Biegel

Pager

2016

J Virol

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During infection, positive-strand RNA viruses subvert cellular machinery involved in RNA metabolism to translate viral proteins and replicate viral genomes to avoid or disable the host defense mechanisms. Cytoplasmic RNA granules modulate the stabilities of cellular and viral RNAs. Understanding how hepatitis C virus and other flaviviruses interact with the host machinery required for protein synthesis, localization, and degradation of mRNAs is important for elucidating how these processes occur in both virus-infected and uninfected cells.T he life of a newly synthesized mRNA would be aimless in the absence of RNA binding proteins (RBPs) and microRNAs. These interactions and the formation of ribonucleoprotein particles (RNPs) direct mRNAs from the nucleus to the cytoplasm for translation or to RNA granules for storage and/or degradation (1). To the benefit or detriment of a virus, viral RNA is equally exposed to such fates. From the time that a virus binds and enters a host cell, the virus interfaces with and frequently subverts different host mRNA metabolism pathways. Hepatitis C virus (HCV) is a master of such mechanisms, efficiently co-opting the cellular translation machinery, the microRNA pathway, and components associated with mRNA storage and decay.The single-stranded positive-sense RNA genome of HCV encodes a single open reading frame. Untranslated regions (UTRs) at the 5= and 3= ends of the genome are highly structured and contain elements that are essential for translation and replication (2). The 5= UTR contains an internal ribosome entry site (IRES) that directly recruits the 40S ribosome and a subset of initiation factors for polyprotein synthesis. Additionally, the liver-specific microRNA miR-122 interacts with two binding sites in the 5= UTR to maintain viral RNA abundance (3). miR-122 was first shown to modestly affect translation and replication (3). However, the most exciting function described for miR-122 was that of shielding the 5= UTR from degradation by the 5=-to-3= exonucleases Xrn1 and Xrn2, thereby increasing the stability of the viral RNA (3). More recently, miR-122 was proposed to facilitate the transition between translation and replication (4), a step that is poorly understood in the life of many viruses. Interestingly, recent work has shown that miR-122 abundance or single point mutations within the miR-122 binding sites facilitate HCV replication independently of miR-122 (5, 6). Many intriguing questions regarding the HCV-miR-122 interaction remain. Although we know that miR-122 must occupy both binding sites to maintain viral RNA abundance, do the sites act independently and synergistically? Does miR-122 binding alter viral RNA structure to affect gene expression, and which RNPs are associated with the miR-122 binding sites? In miR-122-independent gene expression, are the same RNP complexes associated with the HCV 5= UTR, and how are the different phases in the infectious cycle affected? Translation, localization, storage, or destruction of mRNAs is directed by specific RBPs and ...

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“…Importantly, HCV does not hijack the whole RNAi machinery but only some components, in particular AGO2. This is supported by observations that HCV RNA-miR-122 complex reroutes some but not all components of the RNAi machinery to replication foci that are distinct from P bodies (79,80) . In fact, P-body disruption does not alter virus protein levels and virus production (80) .…”

Section: Ago2 and Hepatitis C Virusmentioning

confidence: 78%

“…In fact, P-body disruption does not alter virus protein levels and virus production (80) . Conversely, the HCV RNAs interact with P bodies when cleaved by artificially delivered siRNAs (79) . Together, these results unveil a new function for AGO2 in HCV replication, which (i) is mediated by the miR-122, (ii) probably occurs in a subcellular structures distinct from P bodies, and (iii) is beneficial for the virus.…”

Section: Ago2 and Hepatitis C Virusmentioning

confidence: 99%

RNAi and retroviruses: are they in RISC?

Vasselon¹,

Bouttier²,

Saumet

et al. 2013

BioMolecular Concepts

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RNA interference (RNAi) is a potent cellular system against viruses in various organisms. Although common traits are observed in plants, insects, and nematodes, the situation observed in mammals appears more complex. In mammalian somatic cells, RNAi is implicated in endonucleolytic cleavage mediated by artificially delivered small interfering RNAs (siRNAs) as well as in translation repression mediated by microRNAs (miRNAs). Because siRNAs and miRNAs recognize viral mRNAs, RNAi inherently limits virus production and participates in antiviral defense. However, several observations made in the cases of hepatitis C virus and retroviruses (including the human immunodeficiency virus and the primate foamy virus) bring evidence that this relationship is much more complex and that certain components of the RNAi effector complex [called the RNA-induced silencing complex (RISC)], such as AGO2, are also required for viral replication. Here, we summarize recent discoveries that have revealed this dual implication in virus biology. We further discuss their potential implications for the functions of RNAi-related proteins, with special emphasis on retrotransposition and genome stability.

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Dual regulation of hepatitis C viral RNA by cellular RNAi requires partitioning of Ago2 to lipid droplets and P-bodies

Cited by 26 publications

References 67 publications

HIV-1 Replication and APOBEC3 Antiviral Activity Are Not Regulated by P Bodies

HIV-1 Replication and APOBEC3 Antiviral Activity Are Not Regulated by P Bodies

Hepatitis C Virus Exploitation of Processing Bodies

RNAi and retroviruses: are they in RISC?

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