Vaccinia virus DNA topoisomerase I preferentially removes positive supercoils from DNA

Abstract

Type I DNA topoisomerases homologous to Escherichia coli topoisomerase I normally only remove negative supercoils from DNA. Topoisomerases I from various eukaryotes share sequence homology and remove both positive and negative supercoils from DNA. Here we report that vaccinia virus topoisomerase I has significant difference in substrate preference from the other homologous type I topoisomerases. Vaccinia virus topoisomerase I shows a definite preference for removal of positive supercoiis. In contrast, topoisomerase I from human, wheat germ and Saccharomyces cerevisiae has little preference between positive and negative supercoils. The vaccinia enzyme may have evolved for functions required for optimal viral growth.

Patterns and Mechanisms of Ancestral Histone Protein Inheritance in Budding Yeast

“…Transcription of DNA templates by Pol2 differentially affects supercoiling in front of and behind the passing polymerase, thereby differentially affecting 5′ and 3′ nucleosomes [44],[45]. To assess the role of this activity in 5′ accumulation of old histones, we examined the consequences of inactivation of the major topoisomerase Top1, which in vitro can resolve both negative and positive supercoils [46],[47]. Cells lacking Top1 showed reduced 5′ bias in ancestral nucleosome accumulation (Figure 7E), indicating that resolving DNA topology problems before or after passage of the transcription or replication machinery influences the mobility and/or stability of nucleosomes.…”

Topologies of Complexes Containing O6-Alkylguanine–DNA Alkyltransferase and DNA

“…This is an expected consequence of the preferential binding of vaccinia topoisomerase with positively supercoiled DNA67; 68. When this offset is taken into account, the AGT-dependent linking differences observed with vaccinia and E. coli topoisomerases are fully compatible with each-other (Fig.…”

“… 3 E. coli topoisomerase I preferentially relaxes negatively-supercoiled DNAs while the vaccinia enzyme relaxes both negatively- and positively-supercoiled molecules 66; 67; 68. …”

Fluoroquinolone-dependent DNA Supercoiling by Vaccinia Topoisomerase I

“…We tested this experimentally, noting that Vaccinia topoisomerase I was previously found to relax positive DNA supercoils preferentially ( Figure 6). 34 As expected, incubation of Vaccinia topoisomerase I with relaxed DNA in the presence of ethidium bromide (EtBr), which unwinds DNA w268 upon binding, 35 leads to a distribution of positively supercoiled topoisomers when reactions are terminated without disruption of the drug-DNA interactions ( Figure 6A). Exposure of the reactions to SDS (not shown) or phenol-extraction leads to the expected removal of EtBr and formation of negatively supercoiled topoisomers ( Figure 6B).…”