转录和翻译对大肠杆菌中回旋酶介导的DNA切割的影响。

Effects of transcription and translation on gyrase-mediated DNA cleavage in Escherichia coli.

作者信息

Koo H S, Wu H Y, Liu L F

机构信息

Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.

出版信息

J Biol Chem. 1990 Jul 25;265(21):12300-5.

PMID:2165057

Abstract

Gyrase-mediated DNA cleavage on plasmid DNAs was measured in Escherichia coli treated with oxolinic acid. On pBR322 DNA, gyrase cleavage sites were concentrated in the region between the 3'-ends of the tetA and bla genes. The preferential cleavage in this region was dependent on RNA transcription and the divergent orientation of these two transcription units. The enhanced gyrase cleavage also required translation; chloramphenicol treatment or the insertion of a translation terminator within the 5'-proximal region of the tetA gene abolished the enhanced cleavage. We suggest that the enhanced gyrase cleavage may reflect the changes in local DNA supercoiling during RNA transcription as gyrase cleavage in vitro was shown to be sensitive to the supercoiling state of DNA. The effects of transcription and translation on gyrase cleavage can best be explained by the twin-supercoiled-domain model of transcription (Liu, L. F., and Wang, J. C. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 7024-7027).

摘要

在经恶喹酸处理的大肠杆菌中测定了促旋酶介导的质粒DNA切割情况。在pBR322 DNA上，促旋酶切割位点集中在tetA和bla基因3′端之间的区域。该区域的优先切割取决于RNA转录以及这两个转录单元的发散方向。增强的促旋酶切割也需要翻译；氯霉素处理或在tetA基因5′近端区域内插入翻译终止子会消除增强的切割。我们认为，增强的促旋酶切割可能反映了RNA转录过程中局部DNA超螺旋的变化，因为体外促旋酶切割已被证明对DNA的超螺旋状态敏感。转录和翻译对促旋酶切割的影响可以用转录的双超螺旋结构域模型（Liu, L. F., and Wang, J. C. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 7024 - 7027）来最好地解释。