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  • 1
    Keywords: CELLS ; EXPRESSION ; Germany ; CLONING ; GENE ; PROTEIN ; PROTEINS ; transcription ; RELEASE ; DNA ; FAMILY ; DOMAIN ; CARCINOGENESIS ; CONTRAST ; PARTICLES ; virus ; DEGRADATION ; REPLICATION ; ANTIVIRAL ACTIVITY ; CONSTRUCTION ; IMMUNODEFICIENCY-VIRUS ; RE ; spumaretrovirus ; zoonosis ; cytidine deamination ; HIV-1 VIF ; HYPERMUTATION ; restriction factor ; virion infectivity factor
    Abstract: Genome hypermutation of different orthoretroviruses by cellular cytidine deaminases of the APOBEC3 family during reverse transcription has recently been observed. Lentiviruses like HIV-1 have acquired proteins preventing genome editing in the newly infected cell. Here we show that feline foamy virus (FFV), a typical member of the foamy retrovirus subfamily Spumaretrovirinae, is also refractory to genome deamination. APOBEC3-like FFV genome editing in APOBEC3-positive feline CRFK cells only occurs when the accessory FFV Bet protein is functionally inactivated. Editing of bet-deficient FFV genomes is paralleled by a strong decrease in FFV titer. In contrast to lentiviruses, cytidine deamination already takes place in APOBEC3-positive FFV-producing cells, because edited proviral DNA genomes are consistently present in released particles. By cloning the feline APOBEC3 orthologue, we found that its homology to the second domain of human APOBEC3F is 48%. Expression of feline APOBEC3 in APOBEC3-negative human 293T cells reproduced the effects seen in homologous CRFK cells: Bet-deficient FFV displayed severely reduced titers, high-level genome editing, reduced particle release, and suppressed Gag processing. Although WT Bet efficiently preserved FFV infectivity and genome integrity, it sustained particle release and Gag processing only when fe3 was moderately expressed. Similar to lentiviral Vif proteins, FFV Bet specifically bound feline APOBEC3. In particles from Bet-deficient FFV, feline APOBEC3 was clearly present, whereas its foamy viral antagonist Bet was undetectable in purified WT particles. This is the first report that, in addition to lentiviruses, the foamy viruses also developed APOBEC3-counteracting proteins
    Type of Publication: Journal article published
    PubMed ID: 15911774
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  • 2
    Keywords: CELLS ; CELL ; Germany ; INHIBITION ; PROTEIN ; PROTEINS ; COMPLEX ; MECHANISM ; DOMAIN ; FORM ; PARTICLES ; DEGRADATION ; ANTIVIRAL ACTIVITY ; HIV-1 VIF ; LEUKEMIA-VIRUS ; VIF ; 2 DISTINCT ; ANTIRETROVIRAL DEFENSE ; CYTIDINE DEAMINASES ; EDITING ENZYME APOBEC3G ; MURINE APOBEC3 ; SOCS-BOX ; TYPE-1 VIF
    Abstract: The APOBEC3 cytidine deaminases are part of the intrinsic defense of cells against retroviruses. Lentiviruses and spumaviruses have evolved essential accessory proteins, Vif and Bet, respectively, which counteract the APOBEC3 proteins. We show here that Bet of the Prototype foamy virus inhibits the antiviral APOBEC3C activity by a mechanism distinct to Vif: Bet forms a complex with APOBEC3C without inducing its degradation. Bet abolished APOBEC3C dimerization as shown by co-immunoprecipitation and cross-linking experiments. These findings implicate a physical interaction between Bet and the APOBEC3C. Subsequently, we identified the Bet interaction domain in human APOBEC3C in the predicted APOBEC3C dimerization site. Taken together, these data support the hypothesis that Bet inhibits incorporation of APOBEC3Cs into retroviral particles. Bet likely achieves this by trapping APOBEC3C protein in complexes rendering them unavailable for newly generated viruses due to direct immobilization
    Type of Publication: Journal article published
    PubMed ID: 19074429
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  • 3
    Keywords: RECEPTOR ; CELLS ; EXPRESSION ; CELL ; Germany ; SYSTEM ; PROTEIN ; PROTEINS ; CONTRAST ; TYPE-1 ; virus ; resistance ; HUMAN IMMUNODEFICIENCY VIRUS ; REPLICATION ; sensitivity ; HUMAN-IMMUNODEFICIENCY-VIRUS ; virion infectivity factor ; TRANSMISSION ; DEPLETION ; ENZYME APOBEC3G ; CYTIDINE DEAMINASES ; TYPE-1 VIF ; Type ; DOMESTIC CAT ; ANEMIA VIRUS ; ANTIRETROVIRAL ACTIVITY ; HIV-1 REVERSE TRANSCRIPTION ; PUMA-CONCOLOR
    Abstract: To get more insight into the role of APOBEC3 (A3) cytidine deaminases in the species-specific restriction of feline immunodeficiency virus (FIV) of the domestic cat, we tested the A3 proteins present in big cats (puma, lion, tiger, and lynx). These A3 proteins were analyzed for expression and sensitivity to the Vif protein of FIV. While A3Z3s and A3Z2-Z3s inhibited Delta vif FIV, felid A3Z2s did not show any antiviral activity against Delta vif FIV or wild-type (wt) FIV. All felid A3Z3s and A3Z2-Z3s were sensitive to Vif of the domestic cat FIV. Vif also induced depletion of felid A3Z2s. Tiger A3s showed a moderate degree of resistance against the Vif-mediated counter defense. These findings may imply that the A3 restriction system does not play a major role to prevent domestic cat FIV transmission to other Felidae. In contrast to the sensitive felid A3s, many nonfelid A3s actively restricted wt FIV replication. To test whether Vif(FIV) can protect also the distantly related human immunodeficiency virus type 1 (HIV-1), a chimeric HIV-1. Vif(FIV) was constructed. This HIV-1. VifFIV was replication competent in nonpermissive feline cells expressing human CD4/CCR5 that did not support the replication of wt HIV-1. We conclude that the replication of HIV-1 in some feline cells is inhibited only by feline A3 restriction factors and the absence of the appropriate receptor or coreceptor
    Type of Publication: Journal article published
    PubMed ID: 20444897
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