75 mGy X 射线全身照射激活小鼠免疫细胞转录因子 CREB、NF-kB 及 AP1

ACTIVATION OF TRANSCRIPTION FACTOR CREB AND NF kB IN MURINE IMMUNE CELLS AFTER WBI WITH 75mGy X RAYS

采用凝胶电泳迁移率变化分析和寡核苷酸竞争抑制方法检测小剂量Ｘ射线对小鼠免疫细胞基因转录水平调控的影响。７５ｍＧｙＸ射线全身照射小鼠后４ｈ，脾细胞核蛋白提取物的转录因子ＣＲＥＢ及ＮＦｋＢ与其基因启动部位增强子控制序列的结合活性，分别增强７倍及５倍。胸腺细胞核蛋白提取物ＣＲＥＢ、ＮＦｋＢ及ＡＰ１的结合活性分别增强６倍，４．３倍及２倍。而ＳＰ１、ＧＲＥ及ＯＣＴ１无明显变化。竞争抑制试验证实ＣＲＥＢ及ＮＦｋＢ与控制序列为特异性结合。提示小剂量Ｘ射线全身照射选择性地激活免疫细胞ＣＲＥＢ、ＮＦｋＢ及ＡＰ１，通过与增强子控制序列位点的结合，形成特异的诱导基因转录。

Alterations in transcription factors NF kB, CREB, AP1, SP1, GRE and OCT1 binding to specific known promoter DNA consensus sequences of immune cells from irradiated and sham irradiated mice 4 hours after whole body irradiation (WBI) with 75 mGy X rays were investigated with gel mobility shift assay. Increased binding to NF kB and CREB consensus sequence was found with nuclear extracts prepared from thymocytes and splenocytes of irradiated versus sham irradiated mice. Protein binding to the NF kB consensus sequence by nuclear extracts derived from irradiated mice was 5 fold in splenocytes and 4.3 fold in thymocytes higher than that from sham irradiated. Competition with the cold oligonucleotide containing the consensus suquence for NF kB resulted in loss of the shifed band at 25 fold excess concentration, indicating specific binding. DNA mobility shift assay using CREB consensus sequence showed 7 fold increace in splenocytes and 6 fold increase in thymocytes after low dose radiation (LDR). Competition assays using cold oligonucleotide containing the CREB site eliminated the shift band at 50 fold excess concentration. The binding of AP1 consensus sequence showed a 2 fold increase in thymocyte nuclear extracts after LDR. No changes in protein binding to SP1, GRE and OCT1 consensus sequences were noted. The results indicate that activation of selective transcription factors NF kB, CREB and AP1 of the immune cells in mice occurred after LDR.