期刊
BIOCHEMISTRY
卷 45, 期 38, 页码 11674-11680出版社
AMER CHEMICAL SOC
DOI: 10.1021/bi0520838
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资金
- NCI NIH HHS [5 T32 CA09582, T32 CA009582] Funding Source: Medline
- NICHD NIH HHS [5 T32 HD07043, T32 HD007043] Funding Source: Medline
- NIGMS NIH HHS [GM33944, R01 GM033944-22, R01 GM033944] Funding Source: Medline
Previous studies with human and bacterial topoisomerases suggest that the type II enzyme utilizes two distinct mechanisms to recognize the handedness of DNA supercoils. It has been proposed that the ability of some type II enzymes, such as human topoisomerase II alpha and Escherichia coli topoisomerase IV, to distinguish supercoil geometry during DNA relaxation is mediated by elements in the variable C-terminal domain of the protein. In contrast, the ability of human topoisomerase II alpha and topoisomerase II beta to discern the handedness of supercoils during DNA cleavage suggests that residues in the conserved N-terminal or central domain of the protein are involved in this process. To test this hypothesis, the ability of Paramecium bursaria chlorella virus-1 (PBCV-1) and chlorella virus Marburg-1 (CVM-1) topoisomerase II to relax and cleave negatively and positively supercoiled plasmids was assessed. These enzymes display a high degree of sequence identity with the N-terminal and central domains of eukaryotic topoisomerase II but naturally lack the C-terminal domain. While PBCV-1 and CVM-1 topoisomerase II relaxed under- and overwound substrates at similar rates, they were able to discern the handedness of supercoils during the cleavage reaction and preferentially cut negatively supercoiled DNA. Preferential cleavage was not due to a change in site specificity, DNA binding, or religation. These findings are consistent with a bimodal recognition of DNA geometry in which topoisomerase II uses elements in the C-terminal domain to sense the handedness of supercoils during DNA relaxation and elements in the conserved N-terminal or central domain during DNA cleavage.
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