Substrate specificity plays an important role in uncoupling the catalytic and scaffolding activities of rat testis DNA topoisomerase IIalpha

Bakshi, R and Galande, S and Muniyappa, K (2001) Substrate specificity plays an important role in uncoupling the catalytic and scaffolding activities of rat testis DNA topoisomerase IIalpha. In: Journal of Biomolecular Structure & Dynamics, 18 (5). pp. 749-760.

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Abstract

Topoisomerase II (topo II) is a dyadic enzyme found in all eukaryotic cells. Topo II is involved in a number of cellular processes related to DNA metabolism, including DNA replication, recombination and the maintenance of genomic stability. We discovered a correlation between the development of postnatal testis and increased binding of topo IIalpha to the chromatin fraction. We used this observation to characterize DNA-binding specificity and catalytic properties of purified testis topo IIalpha. The results indicate that topo IIalpha binds a substrate containing the preferred site with greater affinity and, consequently, catalyzes the conversion of form I to form IV DNA more efficiently in contrast to substrates lacking such a site. Interestingly, topo IIalpha displayed high-affinity and cooperativity in binding to the scaffold associated region. In contrast to the preferred site, however, high-affinity binding of topo IIalpha to the scaffold-associated region failed to result in enhanced catalytic activity. Intriguingly, competition assays involving scaffold-associated region revealed an additional DNA-binding site within the dyadic topo IIalpha. These results implicate a dual role for topo IIalpha in vivo consistent with the notion that its sequestration to the chromatin might play a role in chromosome condensation and decondensation during spermatogenesis.

Item Type:	Journal Article
Publication:	Journal of Biomolecular Structure & Dynamics
Publisher:	Adenine Press
Additional Information:	Copyright of this article belongs to Adenine Press.
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	22 Feb 2010 10:13
Last Modified:	04 Jul 2011 11:16
URI:	http://eprints.iisc.ac.in/id/eprint/25635

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