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Genome-wide mapping of Topoisomerase I activity sites reveal its role in chromosome segregation

Rani, Phoolwanti and Nagaraja, Valakunja (2019) Genome-wide mapping of Topoisomerase I activity sites reveal its role in chromosome segregation. In: NUCLEIC ACIDS RESEARCH, 47 (3). pp. 1416-1427.

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Official URL: https://dx.doi.org/10.1093/nar/gky1271


DNA Topoisomerase I (TopoI) in eubacteria is the principle DNA relaxase, belonging to Type 1A group. The enzyme from Mycobacterium smegmatis is essential for cell survival and distinct from other eubacteria in having several unusual characteristics. To understand genome-wide TopoI engagements in vivo, functional sites were mapped by employing a poisonous variant of the enzyme and a newly discovered inhibitor, both of which arrest the enzyme activity after the first transestrification reaction, thereby leading to the accumulation of protein-DNA covalent complexes. The cleavage sites are subsets of TopoI binding sites, implying that TopoI recruitment does not necessarily lead to DNA cleavage in vivo. The cleavage protection conferred by nucleoid associated proteins in vitro suggest a similar possibility in vivo. Co-localization of binding and cleavage sites of the enzyme on transcription units, implying that both TopoI recruitment and function are associated with active transcription. Attenuation of the cleavage upon Rifampicin treatment confirms the close connection between transcription and TopoI action. Notably, TopoI is inactive upstream of the Transcription start site (TSS) and activated following transcription initiation. The binding of TopoI at the Ter region, and the DNA cleavage at the Ter indicates TopoI involvement in chromosome segregation, substantiated by its catenation and decatenation activities.

Item Type: Journal Article
Additional Information: The copyright for this article belongs to the OXFORD UNIV PRESS
Department/Centre: Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited: 03 Jun 2019 10:18
Last Modified: 03 Jun 2019 10:18
URI: http://eprints.iisc.ac.in/id/eprint/62807

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