T Cells Contain an RNase-Insensitive Inhibitor of APOBEC3G Deaminase Activity

PLoS Pathogens

Lorne W Walker¹  Beth K Thielen¹  Garrett W Tomblingson¹  Jaisri R Lingappa¹  Kevin C Klein¹  Mary Rieck²  Jane H Buckner² 

[1] Department of Pathobiology, University of Washington, Seattle, Washington, United States of America;Translational Research Program, Benaroya Research Institute at Virginia Mason, Seattle, Washington, United States of America

关键词: T cells;    Ribonucleases;    Immunoprecipitation;    Epithelial cells;    Oligonucleotides;    Chaperone proteins;    Fluorescence resonance energy transfer;    Hidden Markov models;   

DOI  :  10.1371/journal.ppat.0030135

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

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.

【 授权许可】

CC BY