A role for domain I of the hepatitis C virus NS5A protein in virus assembly

Yin, Chunyong; Goonawardane, Niluka; Stewart, Hazel; Harris, Mark

doi:10.1371/journal.ppat.1006834

Cited by 41 publications

(58 citation statements)

References 82 publications

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“…As shown in Fig 7, there was a noticeable increase in the amount of pS225 reactivity between 24-72 h.p.e. As observed previously (19), over time the size of LDs increased and NS5A became almost exclusively associated with the periphery of these LDs. The distribution of pS225 also associated with the periphery of LDs but was restricted to part of the LDs.…”

Section: Resultssupporting

confidence: 86%

“…This is likely due to an effect on genome replication and is consistent with the 10-fold reduction in replication seen previously with the S225A phosphoablatant mutant (37). We also observed that inhibition of these kinases resulted in a loss of co-localisation of NS5A with LDs, suggesting that this association is required for efficient genome replication, in addition to its requirement for virus assembly (19, 47).…”

Section: Discussionmentioning

confidence: 68%

“…In parallel inhibitor-treated HCV-infected cells were analysed using high resolution confocal microscopy (Airyscan) to examine effects on the subcellular distribution of total NS5A, pS225-NS5A and LDs. The latter were chosen as we, and others, had previously shown co-localisation of NS5A and LD (19, 22, 30, 37, 40, 41), and redistribution of LDs in the context of cells infected with HCV containing the phosphoablatant S225A NS5A mutant (37). Treatment with D4476 resulted in a dose-dependent condensation of NS5A-positive punctae into larger structures, some of which accumulated at the surface of LD, particularly at higher concentrations (Fig 3A).…”

Section: Resultsmentioning

confidence: 99%

“…The domains are linked by low complexity sequences (LCS) I and II (Fig 1A), LCSI is serine-rich, and LCSII is proline-rich. All three domains bind the HCV 3′UTR (18): DI functions in both genome replication and virus assembly (19), DII is exclusively involved in genome replication (20) and DIII plays a critical role in virion assembly (21). NS5A has been shown to associate with lipid droplets (LDs) in infected cells (22), where it is postulated to physically link the processes of genome replication and virus assembly (19).…”

Section: Introductionmentioning

confidence: 99%

“…All three domains bind the HCV 3′UTR (18): DI functions in both genome replication and virus assembly (19), DII is exclusively involved in genome replication (20) and DIII plays a critical role in virion assembly (21). NS5A has been shown to associate with lipid droplets (LDs) in infected cells (22), where it is postulated to physically link the processes of genome replication and virus assembly (19). NS5A also interacts with many cellular proteins (23, 24) and signalling pathways (25-27), modifying the host cell environment to favour the virus, this may require a subset of NS5A distinct from that involved in genome replication or virus assembly.…”

Section: Introductionmentioning

confidence: 99%

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A pivotal role of serine 225 phosphorylation in the function of hepatitis C virus NS5A revealed with the application of a phosphopeptide antiserum and super-resolution microscopy

Goonawardane

Harris

2018

Preprint

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241, importance: 150, main text (excluding figure legends): 4984 Abstract 18NS5A is a multi-functional phosphoprotein that plays a key role in both viral replication 19 and assembly. The identity of the kinases that phosphorylate NS5A, and the 20 consequences for HCV biology, remain largely undefined. We previously identified 21 serine 225 (S225) within low complexity sequence (LCS) I as a major phosphorylation 22 site and used a phosphoablatant mutant (S225A) to define a role for S225 23 phosphorylation in the regulation of genome replication, interactions of NS5A with 24 several host proteins and the sub-cellular localisation of NS5A. To investigate this 25 further, we raised an antiserum to S225 phosphorylated NS5A (pS225). Western blot 26 analysis revealed that pS225 was exclusively found in the hyper-phosphorylated 27 NS5A species. Furthermore, using kinase inhibitors we demonstrated that S225 was 28 phosphorylated by casein kinase 1α (CK1α) and polo-like kinase 1 (PLK1). Using a 29 panel of phosphoablatant mutants of other phosphorylation sites in LCSI we obtained 30 the first direct evidence of bidirectional hierarchical phosphorylation initiated by 31 phosphorylation at S225. 32Using super-resolution microscopy (Airyscan and Expansion), we revealed a unique 33 architecture of NS5A-positive clusters in HCV-infected cells -pS225 was concentrated 34 on the surface of these clusters, close to lipid droplets. Pharmacological inhibition of 35 S225 phosphorylation resulted in the condensation of NS5A-positive clusters into 36 larger structures, recapitulating the S225A phenotype.Although S225 37 phosphorylation was not specifically affected by daclatasvir treatment, the latter also 38 resulted in a similar condensation. These data are consistent with a key role for S225 39 phosphorylation in the regulation of NS5A function. Importance 41 NS5A has obligatory roles in the hepatitis C virus lifecycle, and is proposed to be 42 regulated by phosphorylation. As NS5A is a target for highly effective direct-acting 43 antivirals (DAAs) such as daclatasvir (DCV) it is vital to understand how 44 phosphorylation occurs and regulates NS5A function. We previously identified serine 45 225 (S225) as a major phosphorylation site. Here we used an antiserum specific for 46 NS5A phosphorylated at S225 (pS225-NS5A) to identify which kinases phosphorylate 47 this residue. Using super-resolution microscopy we showed that pS225 was present 48 in foci on the surface of larger NS5A-positive clusters likely representing genome 49 replication complexes. This location would enable pS225-NS5A to interact with cellular 50 proteins and regulate the function and distribution of these complexes. Both loss of 51 pS225 and DCV treatment resulted in similar changes to the structure of these 52 complexes, suggesting that DAA treatment might target a function of NS5A that is also 53 regulated by phosphorylation. 54 56 Hepatitis C virus (HCV) infects an estimated 73 million people and frequently results 57 in chronic liver disease -cirrhosis and he...

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Section: Resultssupporting

confidence: 86%