Aim:To construct an A20 expression vector under the control of mouse osteocalcinpromoter(OC-A20),and investigate osteoblastic MC3T3-EI cell line,whichstably overexpresses A20 protein prevented tumor necrosis factor(TNF)-alpha-induced apoptosis.Methods:OC-A20 vector was constructed by fusing a frag-ment of the mouse osteocalcin gene-2 promoter with human A20 complementaryDNA.Then the mouse MC3T3-E1 cell line,stably transfected by A20,wasestablished.The expression of A20 mRNA and A20 protein in the cells weredetected by reverse transcription-polymerase chain reaction(RT-PCR)and West-ern blot analysis,respectively.To determine the specificity of A20 expression inosteoblast,the mouse osteoblastic MC3T3-E1 cell line and mouse embryo fibro-blast NIH3T3 cell line were transiently transfected with OC-A20.The anti-apoptoticrole of A20 in MC3T3-E1 cells was determined by Flow cytometric analysis(FACS),terminal dUTP nick endo-labeling(TUNEL)and DNA gel electrophoresis analysis(DNA Ladder),respectively.Results:Weak A20 expression was found in MC3T3-E1 cells with the primers of mouse A20.A20 mRNA and A20 protein expressionwere identified in MC3T3-E1 cells transfected with OC-A20 using RT-PCR andWestern blot analysis.Only A20 mRNA expression was found in MC3T3-E1 cellafter MC3T3-E1 cells and NII-/3T3 cells were transient transfected with OC-A20.Adecrease obviously occurred in the rate of apoptosis in the OC-A20 group com-pared with the empty vector(pcDNA3)group by FACS(P<0.001).A significantincrease in TUNEL positive staining was found in the pcDNA group comparedwith OC-A20 group(P<0.001).Simultaneously,similar effects were demonstratedin DNA gel electrophoresis analysis.Conclusion:We constructed an osteoblast-specific expression vector that expressed A20 protein in MC3T3-E1 cells andconfirmed that A20 protects osteoblast against TNF-alpha-induced apoptosis. Aim: To construct an A20 expression vector under the control of mouse osteocalcin promoter (OC-A20), and investigate osteoblastic MC3T3-EI cell line, which stably overexpresses A20 protein prevented tumor necrosis factor (TNF) -alpha- induced apoptosis. Methods: OC- A20 vector was constructed by fusing a frag-ment of the mouse osteocalcin gene-2 ​​promoter with human A20 complementary DNA. The mouse MC3T3-E1 cell line, stably transfected by A20, wasestablished. Expression of A20 mRNA and A20 protein in the cells weredetected by reverse transcription-polymerase chain reaction (RT-PCR) and West-ern blot analysis, respectively. To determine the specificity of A20 expression inosteoblast, the mouse osteoblastic MC3T3-E1 cell line and mouse embryo fibro-blast NIH3T3 cell line were transiently transfected with OC-A20.The anti-apoptotic clone of A20 in MC3T3-E1 cells was determined by Flow cytometric analysis (FACS), terminal dUTP nick endo-labeling (TUNEL) and DNA gel electrophoresis analysis (DNA Ladder), respect We20 A20 expression was found in MC3T3-E1 cells with the primers of mouse A20. A20 mRNA and A20 protein expression identified in MC3T3-E1 cells transfected with OC-A20 using RT-PCR and Western blot analysis. Only A20 mRNA expression was found in the rate of apoptosis in the OC-A20 group com-pared with the empty vector (pcDNA3) group was found in MC3T3-E1 cellafter MC3T3-E1 cells and NII- / 3T3 cells were transiently transfected with OC- by FACS (P <0.001). A significant increase in TUNEL positive staining was found in the pcDNA group compared with OC-A20 group (P <0.001). Simultaneously, similar effects were demonstrated in DNA gel electrophoresis analysis. Confc: We constructed an osteoblast-specific expression vector that expressed A20 protein in MC3T3-E1 cells and confirmed that A20 protects osteoblast against TNF-alpha-induced apoptosis.