伯氏疏螺旋体转录因子BB0025经RuvA/RuvB调控VlsE抗原表达与重组突变实现免疫逃避机制

伯氏疏螺旋体（Bb）可调控VlsE等抗原表达以及VlsE重组突变实现免疫逃逸维持感染状态，介导DNA重组修复的霍利迪连接体分支转移酶RuvA、RuvB与VlsE重组有关，但机制不明。我们发现Bb的YebC家族蛋白BB0025可能是调控RuvA/RuvB和VlsE表达的转录因子，该基因敲除导致RuvA/RuvB和VlsE表达显著下降。本项目拟采用Bb靶基因敲除法以及蜱、免疫正常或缺陷小鼠感染模型，确定BB0025转录因子调控ruvA、ruvB和vlsE基因表达作用，采用EMSA/CHIP等确定重组BB0025转录因子结合ruvA、ruvB、vlsE基因启动子与表达调控方式，比较ruvA或ruvB基因敲除前后VlsE变异频率与速率、VlsE表达区与沉默盒同源重组序列及其相互关系，阐明Bb感染哺乳类宿主时经转录因子BB0025-RuvA/RuvB途径上调VlsE表达与重组实现免疫逃逸分子机制。

Borrelia burgdorferi (Bb) can regulate the antigens expression and recombination mutation of VlsE and VlsE to achieve immune escape and maintain the infection in the host. The holliday ligand branch transferases RuvA and RuvB, which mediate DNA recombination and repair, are related to VlsE recombination, but the mechanism is unclear. We found that the YebC family protein BB0025 of Bb may be a transcription factor that regulates the expression of RuvA/RuvB and VlsE, and knockout this gene led to a significant decrease in the expression of RuvA/RuvB and VlsE. Our project intends to use Bb target gene knockout, ticks infections, and immune defects or normal mice infection model to determine the role of BB0025 transcription factor in regulation of ruvA, ruvB and vlsE expression. We further use EMSA/CHIP to define the mechanism of BB0025 transcription factor binding tp ruvA, ruvB, vlsE gene promoter and expression regulation, and compare the vlsE mutation frequency and rate before and after deletion of ruvA and ruvB. We also analyze the relationship between vlsE express area and silent box of homologous recombination sequences. Together, our project can elucidate the molecular mechanism of immune escape when Bb infects mammalian hosts by upregulation of VlsE expression and recombination via transcription factor BB0025-RuvA/RuvB pathway.