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DNA relaxation mediated by Ustilago maydis type I topoisomerase; modulation by chromatin associated proteins.

TitleDNA relaxation mediated by Ustilago maydis type I topoisomerase; modulation by chromatin associated proteins.
Publication TypeJournal Article
Year of Publication1993
AuthorsThiyagarajan MM, Kotani H, Holloman WK, Kmiec EB
JournalBiochim Biophys Acta
Volume1173
Issue2
Pagination155-64
Date Published1993 May 28
ISSN0006-3002
KeywordsDNA Topoisomerases, Type I, DNA, Superhelical, DNA-Binding Proteins, Fungal Proteins, High Mobility Group Proteins, Histones, Kinetics, Ustilago
Abstract

Ustilago maydis topoisomerase I relaxes superhelical DNA in the absence of any co-factors. The reaction reaches a defined end-point proportional to the amount of enzyme added and an analysis of the reaction by Hill plot transformation indicates that at least two molecules of topoisomerase must interact with the DNA to catalyze relaxation. The addition of purified Ustilago histone H1 reduces the stoichiometric amount of topoisomerase I required by 50%. H1 histone may function to enhance DNA relaxation through a cooperative mechanism. The purified HMG-like protein from Ustilago also enhances DNA relaxation mediated by the topoisomerase. Whereas H1 stimulates topo I-mediated DNA relaxation through a processive mode, the HMG-like protein enhances through a distributive mechanism. Taken together, these results demonstrate that the interaction of chromosomal proteins with topoisomerase can influence DNA topology, and mechanisms are proposed to explain this enhancement.

Alternate JournalBiochim. Biophys. Acta
PubMed ID8389206

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