T cells contain an RNase-insensitive inhibitor of APOBEC3G deaminase activity.
The deoxycytidine deaminase APOBEC3G (A3G) is expressed in human T cells and inhibits HIV-1 replication. When transfected into A3G-deficient epithelial cell lines, A3G induces catastrophic hypermutation by deaminating the HIV-1 genome. Interestingly, studies suggest that endogenous A3G in T cells in...
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2007-09-01
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doaj-dd6a722cf18242ed8be0ae680893f8992020-11-25T01:20:07ZengPublic Library of Science (PLoS)PLoS Pathogens1553-73661553-73742007-09-01391320133410.1371/journal.ppat.0030135T cells contain an RNase-insensitive inhibitor of APOBEC3G deaminase activity.Beth K ThielenKevin C KleinLorne W WalkerMary RieckJane H BucknerGarrett W TomblingsonJaisri R LingappaThe deoxycytidine deaminase APOBEC3G (A3G) is expressed in human T cells and inhibits HIV-1 replication. When transfected into A3G-deficient epithelial cell lines, A3G induces catastrophic hypermutation by deaminating the HIV-1 genome. Interestingly, studies suggest that endogenous A3G in T cells induces less hypermutation than would be expected. However, to date, the specific deaminase activity of endogenous A3G in human CD4+ T cells has not been examined directly. Here, we compared deaminase activity of endogenous and exogenous A3G in various human cell lines using a standard assay and a novel, quantitative, high-throughput assay. Exogenous A3G in epithelial cell lysates displayed deaminase activity only following RNase treatment, as expected given that A3G is known to form an enzymatically inactive RNA-containing complex. Surprisingly, comparable amounts of endogenous A3G from T cell lines or from resting or activated primary CD4+ T cells exhibited minimal deaminase activity, despite RNase treatment. Specific deaminase activity of endogenous A3G in H9, CEM, and other T cell lines was up to 36-fold lower than specific activity of exogenous A3G in epithelial-derived cell lines. Furthermore, RNase-treated T cell lysates conferred a dose-dependent inhibition to epithelial cell lysates expressing enzymatically active A3G. These studies suggest that T cells, unlike epithelial-derived cell lines, express an unidentified RNase-resistant factor that inhibits A3G deaminase activity. This factor could be responsible for reduced levels of hypermutation in T cells, and its identification and blockade could offer a means for increasing antiretroviral intrinsic immunity of T cells.http://europepmc.org/articles/PMC1993843?pdf=render |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Beth K Thielen Kevin C Klein Lorne W Walker Mary Rieck Jane H Buckner Garrett W Tomblingson Jaisri R Lingappa |
spellingShingle |
Beth K Thielen Kevin C Klein Lorne W Walker Mary Rieck Jane H Buckner Garrett W Tomblingson Jaisri R Lingappa T cells contain an RNase-insensitive inhibitor of APOBEC3G deaminase activity. PLoS Pathogens |
author_facet |
Beth K Thielen Kevin C Klein Lorne W Walker Mary Rieck Jane H Buckner Garrett W Tomblingson Jaisri R Lingappa |
author_sort |
Beth K Thielen |
title |
T cells contain an RNase-insensitive inhibitor of APOBEC3G deaminase activity. |
title_short |
T cells contain an RNase-insensitive inhibitor of APOBEC3G deaminase activity. |
title_full |
T cells contain an RNase-insensitive inhibitor of APOBEC3G deaminase activity. |
title_fullStr |
T cells contain an RNase-insensitive inhibitor of APOBEC3G deaminase activity. |
title_full_unstemmed |
T cells contain an RNase-insensitive inhibitor of APOBEC3G deaminase activity. |
title_sort |
t cells contain an rnase-insensitive inhibitor of apobec3g deaminase activity. |
publisher |
Public Library of Science (PLoS) |
series |
PLoS Pathogens |
issn |
1553-7366 1553-7374 |
publishDate |
2007-09-01 |
description |
The deoxycytidine deaminase APOBEC3G (A3G) is expressed in human T cells and inhibits HIV-1 replication. When transfected into A3G-deficient epithelial cell lines, A3G induces catastrophic hypermutation by deaminating the HIV-1 genome. Interestingly, studies suggest that endogenous A3G in T cells induces less hypermutation than would be expected. However, to date, the specific deaminase activity of endogenous A3G in human CD4+ T cells has not been examined directly. Here, we compared deaminase activity of endogenous and exogenous A3G in various human cell lines using a standard assay and a novel, quantitative, high-throughput assay. Exogenous A3G in epithelial cell lysates displayed deaminase activity only following RNase treatment, as expected given that A3G is known to form an enzymatically inactive RNA-containing complex. Surprisingly, comparable amounts of endogenous A3G from T cell lines or from resting or activated primary CD4+ T cells exhibited minimal deaminase activity, despite RNase treatment. Specific deaminase activity of endogenous A3G in H9, CEM, and other T cell lines was up to 36-fold lower than specific activity of exogenous A3G in epithelial-derived cell lines. Furthermore, RNase-treated T cell lysates conferred a dose-dependent inhibition to epithelial cell lysates expressing enzymatically active A3G. These studies suggest that T cells, unlike epithelial-derived cell lines, express an unidentified RNase-resistant factor that inhibits A3G deaminase activity. This factor could be responsible for reduced levels of hypermutation in T cells, and its identification and blockade could offer a means for increasing antiretroviral intrinsic immunity of T cells. |
url |
http://europepmc.org/articles/PMC1993843?pdf=render |
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