Catalytic Polypeptide-like 3G Research Articles

Clinical significance of human endogenous retrovirus K (HERV-K) in multiple myeloma progression.

Human endogenous retroviruses (HERVs) are retrotransposons that infect human germline cells and occupy 5-8% of the human genome. Their expression, though inhibited by mutation, deletion, and epigenetic mechanisms under normal conditions, is associated with diseases including cancer. This study aimed to clarify the association between HERVs and multiple myeloma (MM) progression. We found that HERV-K envelope (env) and long-term repeat (LTR) expression was statistically significantly higher within plasma cells in MM than in monoclonal gammopathy of undetermined significance or controls. HERV-K env knockdown increased proliferation in the MM.1S cell line and decreased the expression of the tumor suppressor genes TP53 and CDKN1A. TP53 and CDKN1A were highly expressed in MM, and their expression was correlated with HERV-K expression. HERV-K knockdown reduced apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3F, 3G, and 3H expression by 10-20% in MM.1S cells. The anti-retroviral agents nevirapine and nelfinavir suppressed proliferation and increased HERV-K expression in MM cell lines. Our results suggest that HERV-K is involved in MM progression, but its role is likely to go beyond promoting cell proliferation. Clarifying the role of HERV-K in MM will lead to the discovery of novel treatment strategies and supply new insights into MM pathogenesis.

Compound IMB-Z inhibits hepatitis B virus replication through increasing APOBEC3G expression and incorporation into viral nucleocapsids

As a host restriction factor, apolipoprotein B messenger RNA-editing enzyme catalytic polypeptide-like 3G (APOBEC3G or A3G) has been shown to suppress the replication of several viruses including hepatitis B virus (HBV). Recently, we reported that IMB-Z, a N-phenylbenzamide derivative, could inhibit Enterovirus 71 replication, and A3G mediated its antiviral activity. Whether IMB-Z exhibits an inhibitory effect on HBV replication has not been investigated. HBV DNA, pregenomic RNA (pgRNA), core protein, and capsid levels were determined by a qPCR assay or Southern blot, Northern blot, Western blot, and particle gel assay, respectively. Mutation analysis of HBV DNAs was conducted by a differential DNA denaturation PCR assay. A3G encapsidation into HBV nucleocapsids was examined by Western blot analysis after ultracentrifugation and a co-immunoprecipitation (IP) assay between HBV core and A3G proteins. In the present study, we found that IMB-Z could considerably inhibit HBV replication in HepAD38 cells. Interestingly, IMB-Z did not alter the HBV pgRNA production but could reduce the level of core protein, viral nucleocapsids, and core-associated DNA, as well as cccDNA intracellular amplification. Similar to the action of IMB-Z's inhibition of Enterovirus 71 replication, we found that IMB-Z's inhibition of HBV replication was associated with increased level of A3G. Mechanistically, we demonstrated that the inhibitory effect of IMB-Z is independent of the cytidine deaminase activity of A3G and is exerted by increasing its incorporation into viral nucleocapsids. Our results indicate that IMB-Z inhibits HBV through pharmacological induction A3G expression and incorporation into HBV nucleocapsids.

Lead optimization to improve the antiviral potency of 2-aminobenzamide derivatives targeting HIV-1 Vif-A3G axis.

The viral infectivity factor (Vif)-apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G (APOBEC3G) axis has been recognized as a valid target for developing novel small-molecule therapies for acquired immune deficiency syndrome (AIDS) or for enhancing innate immunity against viruses. Our previous work reported the novel Vif antagonist 2-amino-N-(2-methoxyphenyl)-6-((4-nitrophenyl)sulfonyl)benzamide (2) with strong antiviral activity. In this work, through optimizations of ring C of 2, we discovered the more potent compound 6m with an EC50 of 0.07μM in non-permissive H9 cells, reflecting an approximately 5-fold enhancement of antiviral activity compared to that of 2. Western blotting indicated that 6m more strongly suppressed the defensive protein Vif than 2at the same concentration. Furthermore, 6m suppressed the replication of various clinical drug-resistant HIV strains (FI, NRTI, NNRTI, IN and PI) with relatively high efficacy. These results suggested that compound 6m is a more potent candidate for treating AIDS.

APOBEC3G rescues cells from the deleterious effects of DNA damage.

Human apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3G (hA3G), a member of the APOBEC family, was described as an anti-HIV-1 restriction factor, deaminating reverse transcripts of the HIV-1 genome. Several types of cancer cells that express high levels of A3G, such as diffuse large B-cell lymphoma cells and glioblastomas, show enhanced cell survival after ionizing radiation and chemotherapy treatments. Previously, we showed that hA3G promotes (DNA) double-strand breaks repair in cultured cells and rescues transgenic mice from a lethal dose of ionizing radiation. Here, we show that A3G rescues cells from the detrimental effects of DNA damage induced by ultraviolet irradiation and by combined bromodeoxyuridine and ultraviolet treatments. The combined treatments stimulate the synthesis of cellular proteins, which are exclusively associated with A3G expression. These proteins participate mainly in nucleotide excision repair and homologous recombination DNA repair pathways. Our results implicate A3G inhibition as a potential strategy for increasing tumor cell sensitivity to genotoxic treatments.

Differentially expressed immune response genes in COVID-19 patients based on disease severity.

Background: Dysregulated immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are thought to underlie the progression of coronavirus disease 2019 (COVID-19). We sought to further characterize host antiviral and cytokine gene expression in COVID-19 patients based on illness severity.Methods: In this case-control study, we retrospectively analyzed 46 recovered COVID-19 patients and 24 healthy subjects (no history of COVID-19) recruited from the Second People's Hospital of Fuyang City. Blood samples were collected from each study participant for RNA extraction and PCR. We assessed changes in antiviral gene expression between healthy controls and patients with mild/moderate (MM) and severe/critical (SC) disease.Results: We found that type I interferon signaling (IFNA2, TLR8, IFNA1, IFNAR1, TLR9, IRF7, ISG15, APOBEC3G, and MX1) and genes encoding proinflammatory cytokines (IL12B, IL15, IL6, IL12A and IL1B) and chemokines (CXCL9, CXCL11 and CXCL10) were upregulated in patients with MM and SC disease. Moreover, we found that IFNA1, apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3G (APOBEC3G), and Fas-associated protein with death domain (FADD) were significantly downregulated (P < 0.05) in the SC group compared to the MM group. We also observed that microRNA (miR)-155 and miR-130a levels were markedly higher in the MM group compared to the SC group.Conclusion: COVID-19 is associated with the activation of host antiviral genes. Induction of the IFN system appears to be particularly important in controlling SARS-CoV-2 infection, as decreased expression of IFNA1, APOBEC3G and FADD genes in SC patients, relative to MM patients, may be associated with disease progression.

USP49 potently stabilizes APOBEC3G protein by removing ubiquitin and inhibits HIV-1 replication.

The antiviral activity of host factor apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3G (APOBEC3G, A3G) and its degradation mediated by human immunodeficiency virus type 1 (HIV-1) Vif protein are important topics. Although accumulating evidence indicates the importance of deubiquitination enzymes (DUBs) in innate immunity, it is unknown if they participate in A3G stability. Here, we found that USP49 directly interacts with A3G and efficiently removes ubiquitin, consequently increasing A3G protein expression and significantly enhancing its anti-HIV-1 activity. Unexpectedly, A3G degradation was also mediated by a Vif- and cullin-ring-independent pathway, which was effectively counteracted by USP49. Furthermore, clinical data suggested that USP49 is correlated with A3G protein expression and hypermutations in Vif-positive proviruses, and inversely with the intact provirus ratio in the HIV-1 latent reservoir. Our studies demonstrated a mechanism to effectively stabilize A3G expression, which could comprise a target to control HIV-1 infection and eradicate the latent reservoir.

Polymorphisms in the APOBEC3G gene of Chinese rhesus macaques affect resistance to ubiquitination and degradation mediated by HIV-2 Vif.

Animal cells have multiple innate effector mechanisms that inhibit viral replication. For the pathogenic retrovirus human immunodeficiency virus 1 (HIV-1), there are widely expressed restriction factors, such as APOBEC3 proteins, tetherin/BST2, SAMHD1 and MX2, as well as TRIM5α. We previously found that the TRIM5α gene clearly affects SIVmac or HIV-2 replication, but the major determinant of the combinatorial effect caused by multiple host restriction factors is still not fully clear. APOBEC3G (apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3G), a host restriction factor that restricts HIV replication by causing cytosine deamination, can be targeted and degraded by the SIV/HIV-1/HIV-2 accessory protein Vif. Although rhesus macaques are widely used in HIV/AIDS research, little is known regarding the impact of APOBEC3G gene polymorphisms on viral Vif-mediated ubiquitin degradation in Chinese-origin rhesus macaques. In this study, we therefore genotyped APOBEC3G in 35 Chinese rhesus macaques. We identified a novel transcript and 27 APOBEC3G polymorphisms, including 20 non-synonymous variants and 7 synonymous mutation sites, of which 10 were novel. According to the predicted structure of the A3G protein, we predicted that the E88K and G212D mutations, both on the surface of the A3G protein, would have a significant effect on Vif-induced A3G degradation. However, an in vitro overexpression assay showed that these mutations did not influence HIV-2-Vif-mediated degradation of APOBEC3G. Unexpectedly, another polymorphism L71R, conferred resistance to Vif-mediated ubiquitin degradation, strongly suggesting that L71R might play an important role in antiviral defense mechanisms.

APOBEC3G is a restriction factor of EV71 and mediator of IMB-Z antiviral activity

Enterovirus 71 (EV71), a single-stranded positive-sense RNA virus, is the causative agent of hand, foot, and mouth disease (HFMD), for which no effective antiviral therapy is currently available. Apolipoprotein B messenger RNA-editing enzyme catalytic polypeptide-like 3G (APOBEC3G or A3G) is a cytidine deaminase that inhibits the replication of several viruses, such as human immunodeficiency virus-1, hepatitis B virus and hepatitis C virus. In our efforts toward understanding the antiviral spectrum and mechanism of A3G, we found that ectopic expression of A3G inhibited EV71 replication, whereas knockdown of endogenous A3G expression promoted EV71 replication. Moreover, inhibition of EV71 replication by IMB-Z, a N-phenylbenzamide derivative, is associated with increased levels of intracellular A3G, but reducing the level of A3G by RNA interference diminished the antiviral activity of IMB-Z. Mechanistically, we obtained evidence suggesting that the cytidine deaminase activity is not required for A3G inhibition of EV71 replication. Instead, we demonstrated that A3G can interact with viral 3D RNA-dependent RNA polymerase (RdRp) and viral RNA and be packaged into progeny virions to reduce its infectivity. Taken together, our results indicate that A3G is a cellular restriction factor of EV71 and mediator of the antiviral activity of IMB-Z. Pharmacological induction and/or stabilization of A3G is a potential therapeutic approach to treat diseases caused by EV71 infection, such as HFMD.

Correlation of Apolipoprotein B mRNA-editing Enzyme, Catalytic Polypeptide- like 3G Genetic Variant rs8177832 with HIV-1 Predisposition in Pakistani Population.

Background: Human immunodeficiency virus (HIV) infection is a global health burden which ultimately results in acquired immune deficiency syndrome (AIDS). There are multiple host fac-tors which are capable of limiting HIV-1 replication. One of the most important host factors which in-hibit HIV-1 DNA synthesis is the apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G (APOBEC3G). Any genetic variation of this important host factor may influence the host suscep-tibility to viral infection.Objective: The aim of the current study was to evaluate any correlation of APOBEC3G genetic varia-tion rs8177832 with HIV-1 infection.Methods: The study involved 142 healthy control and 100 HIV-1 infected subjects. The genetic varia-tion rs8177832 of all studied subjects was determined by allele-specific polymerase chain reaction (AS-PCR).Results: The results showed that the distribution of rs8177832 genotypes AA, AG and GG in healthy subjects and HIV-1 subjects was; 42.253%, 42.957%, 14.788% and 66%, 27%, 7% respectively. Sta-tistical analyses of data showed that there was a significant variation in rs8177832 genotype AA in healthy control and HIV-1 infected subjects (42.257% vs 66%; p-value<0.001).Conclusion: Thus it was concluded that APOBEC3G rs8177832 AA genotype contributes in genetic predisposition to HIV-1 infection in Pakistani population.

Human-APOBEC3G-dependent restriction of porcine endogenous retrovirus replication is mediated by cytidine deamination and inhibition of DNA strand transfer during reverse transcription.

Although human apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3G (APOBEC3G, hA3G)-mediated deamination is the major mechanism used to restrict the infectivity of a broad range of retroviruses, it is unclear whether porcine endogenous retrovirus (PERV) is affected by hA3G or porcine A3F (poA3F). To determine whether DNA deamination is required for hA3G- and poA3F-dependent inhibition of PERV transmission, we developed VSV-pseudotype PERV-B expressing hA3G, mutant hA3G-E67Q (encapsidation and RNA binding activity-deficient), mutant hA3G-E259Q (deaminase-deficient), or poA3F. hA3G-E67Q decreased virus infectivity by ~93% compared to the ~99% decrease of viral infectivity by wild-type hA3G, while hA3G-E259Q decreased the infectivity of PERV-B by ~35%. These data suggest that cytidine deamination activity is crucial for efficient restriction of PERV by hA3G, but cytidine deamination cannot fully explain the inactivation of PERV by hA3G. Furthermore, differential DNA denaturation PCR (3D-PCR) products from 293T cells infected with PERV-B expressing hA3G mutants were sequenced. G-to-A hypermutation was detected at a frequency of 4.1% for hA3G, 3.4% for hA3G-E67Q, and 4.7% for poA3F. These results also suggest that hA3G and poA3F inhibit PERV by a deamination-dependent mechanism. To examine the effect of hA3G on the production of PERV DNA, genomic DNA was extracted from 293T cells 12 h after infection with PERV expressing hA3G, and this DNA was used as template for real-time PCR. A 50% decrease in minus strand strong stop (-sss) DNA synthesis/transfer was observed in the presence of hA3G. Based on these results, we conclude that hA3G may restrict PERV by both deamination-dependent mechanisms and inhibition of DNA strand transfer during PERV reverse transcription.

IL-27 Expression and Responsiveness in Human Uterine Epithelial Cells and Fibroblasts In Vitro and the Role of Estradiol.

Interleukin (IL)-27 is a pleiotropic cytokine that regulates multiple aspects of innate and adaptive immunity, but whose role in immune protection of the female reproductive tract is unknown. Although not constitutively expressed by human uterine epithelial cells and fibroblasts in culture, IL-27 secretion was upregulated after treatment with the viral ligand poly (I:C) in a type I interferon (IFN)-dependent manner, with higher levels measured in fibroblasts than epithelial cells. Estradiol increased poly (I:C)-induced IL-27 production by fibroblasts, but not epithelial cells. While both cell types expressed the IL-27 receptor, only fibroblasts responded to recombinant IL-27 with increased expression of the antiviral genes, APOBEC3G (apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G) and MxA, and the tryptophan-catabolizing enzyme, indoleamine 2,3-dioxygenase (IDO). Estradiol inhibited IL-27-mediated induction of IDO in fibroblasts through estrogen receptor alpha, but had no effect on APOBEC3G. IL-27 pretreatment also potentiated poly (I:C) upregulation of the antiviral genes, OAS2 and APOBEC3G, in fibroblasts. Thus, IL-27 is part of the antiviral response by uterine cells against potential pathogens. The effect of estradiol on IL-27 production and sensitivity by fibroblasts demonstrates a selective hormone action on individual cell types in the uterus and suggests that IL-27 may have differential effects during the menstrual cycle.

Moloney leukemia virus 10 (MOV10) inhibits the degradation of APOBEC3G through interference with the Vif-mediated ubiquitin\u2013proteasome pathway

BackgroundMOV10 protein has ATP-dependent 5′–3′ RNA helicase activity and belongs to the UPF1p superfamily. It can inhibit human immunodeficiency virus type 1 (HIV-1) replication at multiple stages and interact with apolipoprotein-B-mRNA-editing enzyme catalytic polypeptide-like 3G (APOBEC3G or A3G), a member of the cytidine deaminase family that exerts potent inhibitory effects against HIV-1 infection. However, HIV-1-encoded virion infectivity factor (Vif) protein specifically mediates the degradation of A3G via the ubiquitin–proteasome system (UPS).ResultsWe demonstrate that MOV10 counteracts Vif-mediated degradation of A3G by inhibiting the assembly of the Vif-CBF-β-Cullin 5-ElonginB-ElonginC complex. Through interference with UPS, MOV10 enhances the level of A3G in HIV-1-infected cells and virions, and synergistically inhibits the replication and infectivity of HIV-1. In addition, the DEAG-box of MOV10 is required for inhibition of Vif-mediated A3G degradation as the DEAG-box mutant significantly loses this ability.ConclusionsOur results demonstrate a novel mechanism involved in the anti-HIV-1 function of MOV10. Given that both MOV10 and A3G belong to the interferon antiviral system, their synergistic inhibition of HIV-1 suggests that these proteins may play complicated roles in antiviral functions.

Six Highly Conserved Targets of RNAi Revealed in HIV-1-Infected Patients from Russia Are Also Present in Many HIV-1 Strains Worldwide.

RNAi has been suggested for use in gene therapy of HIV/AIDS, but the main problem is that HIV-1 is highly variable and could escape attack from the small interfering RNAs (siRNAs) due to even single nucleotide substitutions in the potential targets. To exhaustively check the variability in selected RNA targets of HIV-1, we used ultra-deep sequencing of six regions of HIV-1 from the plasma of two independent cohorts of patients from Russia. Six RNAi targets were found that are invariable in 82%–97% of viruses in both cohorts and are located inside the domains specifying reverse transcriptase (RT), integrase, vpu, gp120, and p17. The analysis of mutation frequencies and their characteristics inside the targets suggests a likely role for APOBEC3G (apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3G, A3G) in G-to-A mutations and a predominant effect of RT biases in the detected variability of the virus. The lowest frequency of mutations was detected in the central part of all six targets. We also discovered that the identical RNAi targets are present in many HIV-1 strains from many countries and from all continents. The data are important for both the understanding of the patterns of HIV-1 mutability and properties of RT and for the development of gene therapy approaches using RNAi for the treatment of HIV/AIDS.

APOBEC3G governs the generation of truncated AATF protein to ensure oncogenic transformation

The oncogenic potential of Apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3G (APOBEC3G) was recently appreciated by the finding that revealed its ability to downregulate Kruppel-like factor 4 (KLF4) gene translation through its affinity for 3'UTR of KLF4 mRNA. Keeping in view the fact that KLF4 is known to repress apoptosis antagonizing transcription factor (AATF) gene expression, the present study employed stem cells as archetype model to explore the effect of APOBEC3G over-expression upon AATF gene expression within these cells as well as on the genes involved in oncogenic transformation. Such a study revealed that APOBEC3G had the ability to bind AATF mRNA within its third exon to facilitate the generation of truncated 23 kDa AATF translation product which, in turn, had the inherent capacity to be the crucial mediator of APOBEC3G induced oncogenic transformation within such cells.

HIV-1 and hijacking of the host immune system: the current scenario.

Human immunodeficiency virus (HIV) infection is a major health burden across the world which leads to the development of acquired immune deficiency syndrome (AIDS). This review article discusses the prevalence of HIV, its major routes of transmission, natural immunity, and evasion from the host immune system. HIV is mostly prevalent in Sub-Saharan Africa and low income countries. It is mostly transmitted by sharing syringe needles, blood transfusion, and sexual routes. The host immune system is categorized into three main types; the innate, the adaptive, and the intrinsic immune system. Regarding the innate immune system against HIV, the key players are mucosal membrane, dendritic cells (DCs), complement system, interferon, and host Micro RNAs. The major components of the adaptive immune system exploited by HIV are T cells mainly CD4+ T cells and B cells. The intrinsic immune system confronted by HIV involves (apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G) APOBEC3G, tripartite motif 5-α (TRIM5a), terherin, and (SAM-domain HD-domain containing protein) SAMHD1. HIV-1 efficiently interacts with the host immune system, exploits the host machinery, successfully replicates and transmits from one cell to another. Further research is required to explore evasion strategies of HIV to develop novel therapeutic approaches against HIV.

HBV/HIV co-infection and APOBEC3G polymorphisms in a population from Burkina Faso.

BackgroundApolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3G (APOBEC3G) is a potent host defense factor, which interferes with HIV-1 and HBV. Our study had three objectives, to screen a population of HIV-1 infected and uninfected patients in Burkina Faso for HBV, to screen the population for APOBEC3G variants rs6001417, rs8177832, and rs35228531 previously described, and to analyze the effect of these three variants and their haplotypes on HIV-1/HBV co-infection in Burkina Faso.MethodsHBV detection was performed on samples from HIV-1 infected and uninfected subjects using rapid detection tests and real-time PCR. APOBEC3 genotyping was done by the TaqMan allelic discrimination method. Fisher Exact test, Odds ratio (OR), confidence intervals (CI) at 95 %, Linkage disequilibrium (LD) summary statistics and haplotype frequencies were calculated.ResultsThe prevalence of HBV was 56.7 % among HIV-1 positive patients of our study while it was about 12.8 % among HIV-1 seronegative subjects. Genotype E was the genotype of HBV present in our hepatitis B positive samples. Minor allele frequencies of rs6001417, rs8177832, and rs35228531 were higher in seronegative subjects. The T minor allele of variant rs35228531 was protective against HIV-1/HBV co-infection with OR = 0.61, 95 % CI (0.42–0.90), p = 0.013. There was also an association between the GGT haplotype and protection against HIV-1/HBV co-infection, OR = 0.57, 95 % CI (0.33–0.99), p = 0.050. The other haplotypes present in the population were not statistically significant. There minor allele T of the rs35228531 was protective against HIV mono-infection OR = 0.53, 95 % CI (0.3–0.93), P = 0.030. But there was no effect of protection against HBV mono-infection.ConclusionAPOBEC3G through its variants rs6001417, rs8177832, and rs35228531, in this study interferes with HIV-1/HBV co-infection could be due the HIV-1 mono-infection in a population from Burkina Faso.

Zinc-mediated binding of a low-molecular-weight stabilizer of the host anti-viral factor apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G

Apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G (APOBEC3G, A3G), is a human anti-virus restriction protein which works deaminase-dependently and -independently. A3G is known to be ubiquitinated by HIV-1 viral infectivity factor (Vif) protein, leading to proteasomal degradation. A3G contains two zinc ions at the N-terminal domain and the C-terminal domain. Four lysine residues, K297, K301, K303, and K334, are known to be required for Vif-mediated A3G ubiquitination and degradation. Previously, we reported compound SN-1, a zinc chelator that increases steady-state expression level of A3G in the presence of Vif. In this study, we prepared Biotin-SN-1, a biotinylated derivative of SN-1, to study the SN-1–A3G interaction. A pull-down assay revealed that Biotin-SN-1 bound A3G. A zinc-abstraction experiment indicated that SN-1 binds to the zinc site of A3G. We carried out a SN-1–A3G docking study using molecular operating environment. The calculations revealed that SN-1 binds to the C-terminal domain through Zn2+, H216, P247, C288, and Y315. Notably, SN-1-binding covers the H257, E259, C288, and C291 residues that participate in zinc-mediated deamination, and the ubiquitination regions of A3G. The binding of SN-1 presumably perturbs the secondary structure between C288 and Y315, leading to less efficient ubiquitination.

APOBEC3G has the ability to programme T cell plasticity

Recently Apolipoprotein B mRNA editing enzyme, Catalytic Polypeptide-like 3G (APOBEC3G) biology has assumed importance because of its role in oncogenesis. In this context, the present study was addressed to understand the immune-modulatory role of APOBEC3G through its effect upon the T-cell plasticity phenomenon. Such an attempt revealed that APOBEC3G has the inherent capacity to regulate genes coding for STAT3, NF-κB, CCL5, IL-6, IL-4, IFN-γ, IL-10 and IL-17 coupled with downregulation of Treg cells within human peripheral blood mononuclear cells (PBMCs) without any noticeable influence upon CD4+ and CD8+ cell number. On the basis of these findings, we propose that APOBEC3G has the ability to induce T cell plasticity and modulate immune response.

Increased expression with differential subcellular location of cytidine deaminase APOBEC3G in human CD4(+) T-cell activation and dendritic cell maturation.

APOBEC3G (apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3G; A3G) is an innate defense protein showing activity against retroviruses and retrotransposons. Activated CD4(+) T cells are highly permissive for HIV-1 replication, whereas resting CD4(+) T cells are refractory. Dendritic cells (DCs), especially mature DCs, are also refractory. We investigated whether these differences could be related to a differential A3G expression and/or subcellular distribution. We found that A3G mRNA and protein expression is very low in resting CD4(+) T cells and immature DCs, but increases strongly following T-cell activation and DC maturation. The Apo-7 anti-A3G monoclonal antibody (mAb), which was specifically developed, confirmed these differences at the protein level and disclosed that A3G is mainly cytoplasmic in resting CD4(+) T cells and immature DCs. Nevertheless, A3G translocates to the nucleus in activated-proliferating CD4(+) T cells, yet remaining cytoplasmic in matured DCs, a finding confirmed by immunoblotting analysis of cytoplasmic and nuclear fractions. Apo-7 mAb was able to immunoprecipitate endogenous A3G allowing to detect complexes with numerous proteins in activated-proliferating but not in resting CD4(+) T cells. The results show for the first time the nuclear translocation of A3G in activated-proliferating CD4(+) T cells.

Basal transcription of APOBEC3G is regulated by USF1 gene in hepatocyte

Apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3G (APOBEC3G, A3G) exert antiviral defense as an important factor of innate immunity. A variety of cytokines such as IFN-γ、IL2、IL15、IL7 could induce the transcription of A3G. However, the regulation of other nuclear factor on the transcription of A3G have not been reported at the present.To gain new insights into the transcriptional regulation of this restriction factor, we cloned and characterized the promoter region of A3G and investigate the modulation of USF1 gene on the transcription of A3G. We identified a 232 bp region that was sufficient to regulate the activity of full promoter. Transcriptional start sites (TSS) were identified by the luciferase reporter assays of plasmids containing full or shorter fragments of the A3G promoter. The results demonstrated that the core promoter of A3G is located within the region -159/-84 relative to the TSS. Transcriptional activity of A3G core promoter regulated by USF1 was dependent on an E-box (located at position -91/-86 relative to the major TSS) and was abolished after mutation of this DNA element. USF1 gene can take part in basal transcription regulation of the human A3G gene in hepatocyte, and the identified E-box represented a binding site for the USF1.