大肠杆菌topA^-细胞中tetA-cfaABCE的高效转录促进DNA凝集  

DNA Condensation Induced by Transciption of tet A-cfa ABCE in Escherichia coli topA Mutant

作　　者：赵舒怡 张臻峰[2] 黄熙泰[3] 

机构地区：[1]国家电网技术学院泰山校区,山东泰安271000 [2]中国科学院微生物研究所微生物前期开发国家重点实验室,北京100101 [3]南开大学生命科学院,天津300071

出　　处：《中山大学学报（自然科学版）》2015年第6期19-26,共8页Acta Scientiarum Naturalium Universitatis Sunyatseni

基　　金：国家自然科学基金资助项目(30900023;31270124)

摘　　要：为深入了解大肠杆菌top A-突变体中转录对DNA结构的影响,以编码一个tet A-cfa ABCE共转录单元的质粒p JGX15A为研究对象,利用氯喹-琼脂糖凝胶电泳比较了大肠杆菌HB101(top A+,gyr B+)与DM800(top A-,gyr B225)细胞中p JGX15A质粒的拓扑结构状态,发现DM800细胞中p JGX15A存在一种特殊的凝集结构。这种结构在氯喹-琼脂糖凝胶电泳中具有较高的迁移率,而且呈现"弥散"状态而不是清晰的拓扑条带。进一步的研究表明培养基中的四环素质量浓度以及细胞生长时相均会影响p JGX15A在DM800细胞中的结构,而凝集结构只出现在四环素质量浓度低于6μg/m L时的对数期DM800细胞中。原子力显微镜照片显示这种结构并非典型的互缠式超螺旋结构,而是含有不同程度的分子内凝集,部分DNA分子高度凝集为一团。To learn more about the effects of transcription on DNA structure in E. coli top A^-mutant,the plasmid p JGX15 A,carrying a tandem transcription unit of tet A^- cfa ABCE,was used as the reporter plasmid. The topology of p JGX15 A from HB101（ top A^＋,gyr B^＋） and DM800（ top A^-,gyr B225） cells was then analyzed by chloroquine agarose gel electrophoresis. And,a type of irregular condensed structures of p JGX15 A was found in DM800 cells. The condensed plasmid DNA had a high mobility rate and appeared to be smear bands in agarose gel electrophoresis. The topology of p JGX15 A was also greatly affected by both cell growth phase and concentration of tetracycline in medium. The condensed structures were only formed in DM800 cells of exponential phase cultured in the medium with the concentration of tetracycline below 6 μg / m L. AFM images showed that these plasmid DNA molecules contained intra-molecular conde nsation to different levels instead of normal supercoils. Some of the molecules were even completely condensed to a coil.

关 键 词：DNA凝集 转录 原子力显微镜 大肠杆菌 top A-突变株 

分 类 号：Q523[生物学—生物化学]