ABSTRACT
Objective@#To assess the effect of viral macrophage inflammatory protein (vMIP) -Ⅱ on the expression of apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3G (APOBEC3G) , and to explore the mechanisms.@*Methods@#A recombinant plasmid pEGFP-N3-K4 (vMIP-Ⅱ plasmid group) and an empty plasmid pEGFP-N3 (empty plasmid group) were separately transfected into 293T cells, and quantitative PCR and Western blot analysis were performed to evaluate the effect of transfection with vMIP-Ⅱ gene on the APOBEC3G expression in 293T cells. Some 293T cells in the empty plasmid group and vMIP-Ⅱ plasmid group were treated with 1 000 IU/ml interferon (IFN) -α for 36 hours, and then Western blot analysis was conducted to determine the APOBEC3G expression in the empty plasmid group and vMIP-Ⅱ plasmid group with or without IFN-α treatment. Some 293T cells transfected with vMIP-Ⅱ plasmids were treated with 75 μmol/L AG490 (a JAK/STAT signaling pathway inhibitor) and 20 μmol/L U0126 (an ERK signaling pathway inhibitor) separately; after 24 hours, total protein was extracted from 293T cells, and Western blot analysis was conducted to determine the expression of APOBEC3G. A recombinant plasmid containing APOBEC3G promoter was constructed by using a luciferase reporter gene, and the promoter fragment included the full-length promoter sequence (POS) of APOBEC3G, sequences with the lengths of 1 560, 960, 720, 480, 420, 360, 330 and 240 bp, and the regulatory element-free region (NEG) of APOBEC3G, separately. Some 293T cells were co-transfected with the recombinant plasmid carrying luciferase reporter gene and vMIP-Ⅱ plasmid (experimental group), or the recombinant plasmid and empty plasmid (control group). Subsequently, the activity of the APOBEC3G promoter was evaluated, and the key promoter region through which the transcriptional activity of APOBEC3G was regulated by vMIP-Ⅱ was analyzed. Statistical analysis was carried out by using t test, one-way analysis of variance and least significant difference (LSD) -t test.@*Results@#The mRNA and protein expression of APOBEC3G was significantly higher in the vMIP-Ⅱ plasmid group (2.500 ± 0.013, 1.472 ± 0.013 respectively) than in the control group (1, 0.364 ± 0.030 respectively; t = 6.22, 6.54 respectively, both P < 0.05) . The APOBEC3G expression significantly differed among the empty plasmid group, vMIP-Ⅱ plasmid group, empty plasmid + IFN-α group and vMIP-Ⅱ plasmid + IFN-α group (1, 2.030 ± 0.108, 2.700 ± 0.081 and 2.600 ± 0.099 respectively; F = 67.026, P < 0.001) , but there was no significant difference between the vMIP-Ⅱ plasmid group and empty plasmid + IFN-α group (t = 3.46, P > 0.05) . The APOBEC3G expression also significantly differed among the vMIP-Ⅱ plasmid group, vMIP-Ⅱ plasmid + AG490 group and vMIP-Ⅱ plasmid + U0126 group (0.617 ± 0.025, 0.179 ± 0.061, 0.359 ± 0.012 respectively; F = 70.019, P < 0.001) , and was significantly lower in the vMIP-Ⅱ plasmid + AG490 group and vMIP-Ⅱ plasmid + U0126 group than in the vMIP-Ⅱ plasmid group (t = 9.66, 11.836 respectively, both P < 0.01) . Luciferase activity assay showed that the promoter activity significantly differed among the vMIP-Ⅱ plasmid groups transfected with POS, 1 560-, 960-, 720-, 480-, 420-, 360-, 330-, 240-bp or NEG sequences (F = 81.092, P < 0.001) , and the APOBEC3G promoter activity decreased greatly from the 720-bp group to 480-bp group.@*Conclusion@#vMIP-Ⅱ upregulates the expression of APOBEC3G, likely through the JAK/STAT signaling pathway or the key promoter region regulating the transcriptional activity of APOBEC3G.
ABSTRACT
Objective To assess the effect of viral macrophage inflammatory protein (vMIP)-Ⅱ on the expression of apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3G (APOBEC3G),and to explore the mechanisms.Methods A recombinant plasmid pEGFP-N3-K4 (vMIP-Ⅱ plasmid group) and an empty plasmid pEGFP-N3 (empty plasmid group) were separately transfected into 293T cells,and quantitative PCR and Western blot analysis were performed to evaluate the effect of transfection with vMIP-]Ⅱ gene on the APOBEC3G expression in 293T cells.Some 293T cells in the empty plasmid group and vMIP-Ⅱ plasmid group were treated with 1 000 IU/ml interferon (IFN)-α for 36 hours,and then Western blot analysis was conducted to determine the APOBEC3G expression in the empty plasmid group and vMIP-Ⅱ plasmid group with or without IFN-α treatment.Some 293T cells transfected with vMIP-Ⅱplasmids were treated with 75 μ mol/L AG490 (a JAK/STAT signaling pathway inhibitor) and 20 μ mol/L U0126 (an ERK signaling pathway inhibitor) separately;after 24 hours,total protein was extracted from 293T cells,and Western blot analysis was conducted to determine the expression of APOBEC3G.A recombinant plasmid containing APOBEC3G promoter was constructed by using a luciferase reporter gene,and the promoter fragment included the full-length promoter sequence (POS) of APOBEC3G,sequences with the lengths of 1 560,960,720,480,420,360,330 and 240 bp,and the regulatory element-free region (NEG) of APOBEC3G,separately.Some 293T cells were co-transfected with the recombinant plasmid carrying luciferase reporter gene and vMIP-Ⅱ plasmid (experimental group),or the recombinant plasmid and empty plasmid (control group).Subsequently,the activity of the APOBEC3G promoter was evaluated,and the key promoter region through which the transcriptional activity of APOBEC3G was regulated by vMIP -Ⅱ was analyzed.Statistical analysis was carried out by using t test,one-way analysis of variance and least significant difference (LSD)-t test.Results The mRNA and protein expression of APOBEC3G was significantly higher in the vMIP-Ⅱ plasmid group (2.500 ± 0.013,1.472 ± 0.013 respectively) than in the control group (1,0.364 ± 0.030 respectively;t =6.22,6.54 respectively,both P ＜ 0.05).The APOBEC3G expression significantly differed among the empty plasmid group,vMIP-Ⅱ plasmid group,empty plasmid + IFN-oα group and vMIP-Ⅱ plasmid + IFN-α group (1,2.030 ± 0.108,2.700 ± 0.081 and 2.600 ± 0.099 respectively;F =67.026,P ＜ 0.001),but there was no significant difference between the vMIP-Ⅱ plasmid group and empty plasmid + IFN-α group (t =3.46,P ＞ 0.05).The APOBEC3G expression also significantly differed among the vMIP-Ⅱ plasmid group,vMIP-Ⅱ plasmid + AG490 group and vMIP-Ⅱplasmid + U0126 group (0.617 ± 0.025,0.179 ± 0.061,0.359 ± 0.012 respectively;F =70.019,P ＜ 0.001),and was significantly lower in the vMIP-Ⅱ plasmid + AG490 group and vMIP-Ⅱ plasmid + U0126 group than in the vMIP-Ⅱ plasmid group (t =9.66,11.836 respectively,both P ＜ 0.01).Luciferase activity assay showed that the promoter activity significantly differed among the vMIP-Ⅱ plasmid groups transfected with POS,1 560-,960-,720-,480-,420-,360-,330-,240-bp or NEG sequences (F =81.092,P ＜ 0.001),and the APOBEC3G promoter activity decreased greatly from the 720-bp group to 480-bp group.Conclusion vMIP-Ⅱ upregulates the expression of APOBEC3G,likely through the JAK/STAT signaling pathway or the key promoter region regulating the transcriptional activity of APOBEC3G.
ABSTRACT
SDF-1α,a ligand for the chemokine receptor CXCR4,is well known for mediating the migration of breast cancer cells.In a previous study we demonstrated that a synthetic 21-mer peptide antagonist of CXCR4 (NT21MP) derived from the viral macrophage inflammatory protein Ⅱ could antagonize tumor growth in vivo by inhibiting cellular proliferation and inducing apoptosis in breast cancer cells.However,the role of SDF-lα in the signaling pathways underlying the proliferation of human breast cancer cells and associated signaling pathways and inhibiting signal pathways of NT21MP remained unclear.The present study investigated the mechanism of NT21MP on anti-tumor in breast cancer in vitro.The effect of NT21MP on the viability of cells was determined by the MTT assay.Annexin V-FITC and PI staining was performed to detect early stage apoptosis in SKBR3 cells treated with SDF-1α and AMD3100 or NT21MP.Western blotting techniques were used to assay the composition of phosphoproteomics and total proteins present in the SKBR3 breast cancer cells.RT-PCR and Western blotting technique were used to detect the effect of NT21MP and AMD3100 on Bcl-2 and Bax expression.The results indicated that SDF-1α prevented apoptosis and promoted the proliferation of SKBR3 human breast cancer cells.As compared with untreated SKBR3 cells,Treatment with SDF-1α significantly increased cell viability,and NT21MP abolished the protective effects of SDF-1α dose-dependently (P＜0.05).There was a significant decrease in the percentage of apoptotic cells after SDF-lα treatment as compared with control group (2.7％±0.2％ vs.5.7％±0.4％,P＜0.05).But pretreatment of SKBR3 cells with NT21MP significantly attenuated the antiapoptotic effects of SDF-1αt as compared with SKBR3 cells without NT21MP pretreatment.The proliferative and anti-apoptotic effects of SDF-1α in SKBR3 cells were associated with an increase in AKT and ERK1/2 phosphorylation as well as a decrease in Bax expression and an increase in Bcl-2 expression.These changes in intracellular processes were blocked by NT21MP in a dose-dependent manner(P＜0.05).In conclusion,NT21MP efficiently inhibits SDF-1α-induced proliferation and antiapoptosis in SKBR3 cells by reducing the levels of phosphorylated AKT and ERK1/2,as well as decreasing the ratio of expression of Bcl-2 relative to Bax.
ABSTRACT
Objective To clarify the combined ability of viral macrophage inflammatory protein (vMIP) to receptors through comparison research of vMIP binding to chemokine receptors of peripheral blood macrophages(PBMCs). Methods Combined ability of vMIP to receptors was measured with radioligand assay and identified with saturation, kinetic and specificity analyses. Results Kd is 11.1 nmol/L to human receptors of PBMC and 14.3 nmol/L to monkey receptors. The IC50 is 3.4 nmol/L to CCR5 and 4.5 nmol/L to CXCR4. Conclusion vMIP has high affinity with receptors and high specificity to CCR5 and CXCR4.This may be of great significance in the prevention and treatment of inflammation and HIV infection.