ABSTRACT
Objective To investigate whether cyclic GMP-AMP synthase ( cGAS ) , a cytosolic DNA sensor, could recognize the reverse transcription intermediate and induce the subsequent signaling path-way during the infection of human T cell leukemia virus type 1 ( HTLV-1 ) . Methods Biotin-labeled ssDNA90, a reverse transcription intermediate of HTLV-1, was transfected into HeLa cells and the interac-tion between it and cGAS was detected by co-immunoprecipitation experiments. HeLa cells were co-cultured with HTLV-1-positive MT2 cells and the interaction between cGAS and stimulator of interferon genes ( STING) was analyzed by co-immunoprecipitation experiments. The expression of STING in HeLa cells was silenced by siRNA. cGAS was transfected into the HeLa cells 24 h after the silencing and after 24 h, these cells were co-cultured with MT2 cells for another 24 h. Real-time PCR assay was used to measure the ex-pression of IFN-β, RANTES ( regulated upon activation, normal T-cell expressed, and secreted) , TNF-α, HTLV-1 protein Tax, p19 and HBZ. Immunoblot assay was performed to evaluate the phosphorylation of IRF3 and p65 in HeLa cells. Results cGAS interacted with ssDNA90. cGAS interacted with STING in the cytoplasm. In STING-silenced HeLa cells, cGAS transfection had no influence on the expression of IFN-β, RANTES , TNF-α, Tax , p19 or HBZ , nor did it affect the phosphorylation of IRF3 or p65 . Conclusions cGAS interacted with HTLV-1 RTI ssDNA90 and activated STING-dependent innate immune responses.
ABSTRACT
Objective@#To investigate the effects of interferon inducible protein 16 (IFI16), a cytosolic DNA sensor, on the expression of human T-cell leukemia virus type 1 (HTLV-1) proteins and pro-inflammatory cytokines in adult HTLV-1-positive T cells.@*Methods@#IFI16 expression in different HTLV-1-positive T cell lines was detected by immunoblot assay. Specific siRNA targeting the IFI16 gene was constructed and the gene silencing efficiency was detected by immunoblot assay. Expression of HTLV-1 Tax protein at mRNA and protein levels was respectively detected by real-time PCR and immunoblot assay after knocking down the expression of IFI16 in HTLV-1-positive T cells with siRNA. Expression of interferon (IFN)-α, IFN-γ, tumor necrosis factor (TNF)-α, Tax and Env were detected by real-time PCR.@*Results@#Compared with the HTLV-1-negative T cell line Jurkat, IFI16 expression was enhanced in the HTLV-1-positive T cell lines MT2, MT4 and C8166. Tax expression was increased, while that of IFN-α, IFN-γ and TNF-α was decreased in MT2 and MT4 cells after silencing the expression of IFI16 with siRNA.@*Conclusions@#IFI16 expression was increased in HTLV-1-positive MT2 and MT4 cells. Meanwhile, IFI16 promoted the production of interferon and pro-inflammatory cytokines and inhibited the expression of HTLV-1 proteins.
ABSTRACT
Objective To investigate the effects of interferon inducible protein 16 (IFI16), a cy-tosolic DNA sensor, on the expression of human T-cell leukemia virus type 1 (HTLV-1) proteins and pro-in-flammatory cytokines in adult HTLV-1-positive T cells. Methods IFI16 expression in different HTLV-1-positive T cell lines was detected by immunoblot assay. Specific siRNA targeting the IFI16 gene was con-structed and the gene silencing efficiency was detected by immunoblot assay. Expression of HTLV-1 Tax pro-tein at mRNA and protein levels was respectively detected by real-time PCR and immunoblot assay after knocking down the expression of IFI16 in HTLV-1-positive T cells with siRNA. Expression of interferon ( IFN)-α, IFN-γ, tumor necrosis factor ( TNF )-α, Tax and Env were detected by real-time PCR. Re-sults Compared with the HTLV-1-negative T cell line Jurkat, IFI16 expression was enhanced in the HTLV-1-positive T cell lines MT2, MT4 and C8166. Tax expression was increased, while that of IFN-α, IFN-γand TNF-α was decreased in MT2 and MT4 cells after silencing the expression of IFI16 with siRNA. Con-clusions IFI16 expression was increased in HTLV-1-positive MT2 and MT4 cells. Meanwhile, IFI16 pro-moted the production of interferon and pro-inflammatory cytokines and inhibited the expression of HTLV-1 proteins.
ABSTRACT
Objective To investigate the role of cyclic GMP-AMP synthase (cGAS),a cytosolic DNA sensor,in regulating innate immune responses induced by reverse transcription intermediate of human T cell leukemia virus type 1 (HTLV-1). Methods (1)ssDNA90,the reverse transcription intermediate of HTLV-1,was transfected into HeLa cells to observe changes in the expression pattern of cGAS in transfected-HeLa cells with immunoblot assay. (2) HeLa cells were firstly transfected with cGAS-encoding plasmid and then ssDNA90 24 hours later. Real-time PCR was used to measure the expression of interferon ( IFN)-β, IFN-gamma-inducible protein 10 ( IP-10 ), regulated on activation, normal T cell expressed and secreted (RANTES) and tumor necrosis factor (TNF)-α. Immunoblot assay was performed to measure phosphorylated interferon regulatory factor 3 (IRF3) and p65. (3)cGAS expression was silenced by siRNA in HeLa and phorbol-12-myristate-13-acetate (PMA)-treated THP1 (PMA-THP1) cells and then ssDNA90 was transfect-ed into these cells 24 hours later. Real-time PCR was used to measure the expression of IFN-β,IP-10,RAN-TES and TNF-α. Immunoblot assay was performed to measure phosphorylated IRF3 and p65. Results Ex-pression of cGAS was increased in HeLa cells after ssDNA90 transfection. Compared with control cells, cGAS-transfected HeLa cells showed increased expression of IFN-β, IP-10, RANTES and TNF-α and en-hanced phosphorylation of IRF3 and p65 after ssDNA90 transfection. Compared with control cells,both HeLa and PMA-THP1 cells with silenced expression of cGAS showed impaired production of IFN-β,IP-10,RAN-TES and TNF-α after ssDNA90 transfection. Moreover,ssDNA90-induced phosphorylation of IRF3 and p65 were decreased after cGAS gene-knockdown. Conclusion cGAS might promote HTLV-1 RTI ssDNA90-in-duced innate immune responses.
ABSTRACT
Objective To investigate the function and the possible mechanism of cyclic GMP-AMP synthase (cGAS), a DNA sensor, in HeLa cells during human T cell leukemia virus type 1 (HTLV-1) in-fection.Methods HeLa cells were co-cultured with MT2 cells (HTLV-1-positive T cells) and then detec-ted by immunoblot assay to analyze the changes in the expression of cGAS .A hemagglutinin ( HA)-tagged cGAS plasmid was constructed and transfected into HeLa cells .Twenty-four hours after transfection , these cells were co-cultured with MT2 cells for another 24 hours.Immunoblot assay was used to detect the expres-sion of HTLV-1 proteins Tax and p19.Real-time PCR was performed to measure the expression of HTLV-1 Tax, p19, Env, HBZ and px at mRNA level .Immunoblot assay was also used to analyze the phosphorylation of interferon regulatory factor 3 (IRF3) and p65.Expression of interferon (IFN)-β, IFN-gamma-inducible protein 10 ( IP-10 ) , RANTES ( regulated on activation , normal T cell expressed and secreted ) and tumor necrosis factor (TNF)-αwas detected by real-time PCR assay.Results Expression of cGAS was enhanced in HeLa cells after co-cultured with MT2 cells.Compared with control cells , the HeLa cells that were trans-fected with cGAS plasmid showed lower levels of Tax and p 19 proteins, suppressed expression of HTLV-1 Tax, p19, Env, HBZ and px at mRNA level , enhanced phosphorylation of IRF 3 and p65, and higher levels of IFN-β, IP-10, RANTES and TNF-αafter co-cultured with MT2 cells.Conclusion cGAS might promote the innate immune response and inhibit HTLV-1 replication in HTLV-1-infected HeLa cells .