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A link between translation of the hepatitis C virus polyprotein and polymerase function; possible consequences for hyperphosphorylation of NS5A

A link between translation of the hepatitis C virus polyprotein and polymerase function; possible consequences for hyperphosphorylation of NS5A
A link between translation of the hepatitis C virus polyprotein and polymerase function; possible consequences for hyperphosphorylation of NS5A
Hyperphosphorylation of NS5A is thought to play a key role in controlling hepatitis C virus (HCV) RNA replication. Using a tetracycline-regulable baculovirus delivery system to introduce non-culture-adapted HCV replicons into HepG2 cells, we found that a point mutation in the active site of the viral polymerase, NS5B, led to an increase in NS5A hyperphosphorylation. Although replicon transcripts lacking elements downstream of NS5A also had altered NS5A hyperphosphorylation, this did not explain the changes resulting from polymerase inactivation. Instead, two additional findings may be related to the link between polymerase activity and NS5A hyperphosphorylation. Firstly, we found that disabling polymerase activity, either by targeted mutation of the polymerase active site or by use of a synthetic inhibitor, stimulated translation from the replicon transcript. Secondly, when the rate of translation of non-structural proteins from replicon transcripts was reduced by use of a defective encephalomyocarditis virus internal ribosome entry site, there was a substantial decrease in NS5A hyperphosphorylation, but this was not observed when non-structural protein expression was reduced by simply lowering replicon transcript levels using tetracycline.
Therefore, one possibility is that the point mutation within the active site of NS5B causes an increase in NS5A hyperphosphorylation because of an increase in translation from each viral transcript. These findings represent the first demonstration that NS5A hyperphosphorylation can be modulated without use of kinase inhibitors or mutations within non-structural proteins and, as such, provide an insight into a possible means by which HCV replication is controlled during a natural infection.
93-102
McCormick, Christopher J.
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Brown, David
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Griffin, Stephen
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Challinor, Lisa
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Rowlands, David J.
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Harris, Mark
065415f3-96a7-443c-91b4-f75a5945f82b
McCormick, Christopher J.
0fce14bf-2f67-4d08-991f-114dd1e7f0bd
Brown, David
68e8f8ee-6aaf-45e4-9aee-7f76e39ddefe
Griffin, Stephen
49c409b7-ee50-4809-b6b8-d5e192ff7424
Challinor, Lisa
165ef52b-3bef-4d25-aebd-056ca3154b28
Rowlands, David J.
2de54fdc-5f4f-40f3-b259-c8fb966a782a
Harris, Mark
065415f3-96a7-443c-91b4-f75a5945f82b

McCormick, Christopher J., Brown, David, Griffin, Stephen, Challinor, Lisa, Rowlands, David J. and Harris, Mark (2006) A link between translation of the hepatitis C virus polyprotein and polymerase function; possible consequences for hyperphosphorylation of NS5A. The Journal of General Virology, 87 (Pt 1), 93-102. (doi:10.1099/vir.0.81180-0).

Record type: Article

Abstract

Hyperphosphorylation of NS5A is thought to play a key role in controlling hepatitis C virus (HCV) RNA replication. Using a tetracycline-regulable baculovirus delivery system to introduce non-culture-adapted HCV replicons into HepG2 cells, we found that a point mutation in the active site of the viral polymerase, NS5B, led to an increase in NS5A hyperphosphorylation. Although replicon transcripts lacking elements downstream of NS5A also had altered NS5A hyperphosphorylation, this did not explain the changes resulting from polymerase inactivation. Instead, two additional findings may be related to the link between polymerase activity and NS5A hyperphosphorylation. Firstly, we found that disabling polymerase activity, either by targeted mutation of the polymerase active site or by use of a synthetic inhibitor, stimulated translation from the replicon transcript. Secondly, when the rate of translation of non-structural proteins from replicon transcripts was reduced by use of a defective encephalomyocarditis virus internal ribosome entry site, there was a substantial decrease in NS5A hyperphosphorylation, but this was not observed when non-structural protein expression was reduced by simply lowering replicon transcript levels using tetracycline.
Therefore, one possibility is that the point mutation within the active site of NS5B causes an increase in NS5A hyperphosphorylation because of an increase in translation from each viral transcript. These findings represent the first demonstration that NS5A hyperphosphorylation can be modulated without use of kinase inhibitors or mutations within non-structural proteins and, as such, provide an insight into a possible means by which HCV replication is controlled during a natural infection.

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Published date: 2006

Identifiers

Local EPrints ID: 27265
URI: http://eprints.soton.ac.uk/id/eprint/27265
PURE UUID: fab4c656-5130-4c64-9e19-c6a72cd15f51
ORCID for Christopher J. McCormick: ORCID iD orcid.org/0000-0002-6155-9161

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Date deposited: 26 Apr 2006
Last modified: 16 Mar 2024 03:47

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Contributors

Author: David Brown
Author: Stephen Griffin
Author: Lisa Challinor
Author: David J. Rowlands
Author: Mark Harris

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