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Changing Perspectives on the Role of DnaA-ATP in Orisome Function and Timing Regulation

dc.contributor.authorLeonard, Alan C.
dc.contributor.authorRao, Prassanna
dc.contributor.authorKadam, Rohit P.
dc.contributor.authorGrimwade, Julia E.
dc.identifier.citationLeonard AC, Rao P, Kadam RP and Grimwade JE (2019) Changing Perspectives on the Role of DnaA-ATP in Orisome Function and Timing Regulation. Front. Microbiol. 10:2009. doi: 10.3389/fmicb.2019.02009en_US
dc.description.abstractBacteria, like all cells, must precisely duplicate their genomes before they divide. Regulation of this critical process focuses on forming a pre-replicative nucleoprotein complex, termed the orisome. Orisomes perform two essential mechanical tasks that configure the unique chromosomal replication origin, oriC to start a new round of chromosome replication: (1) unwinding origin DNA and (2) assisting with loading of the replicative DNA helicase on exposed single strands. In Escherichia coli, a necessary orisome component is the ATP-bound form of the bacterial initiator protein, DnaA. DnaA-ATP differs from DnaA-ADP in its ability to oligomerize into helical filaments, and in its ability to access a subset of low affinity recognition sites in the E. coli replication origin. The helical filaments have been proposed to play a role in both of the key mechanical tasks, but recent studies raise new questions about whether they are mandatory for orisome activity. It was recently shown that a version of E. coli oriC (oriC(allADP)), whose multiple low affinity DnaA recognition sites bind DnaA-ATP and DnaA-ADP similarly, was fully occupied and unwound by DnaA-ADP in vitro, and in vivo suppressed the lethality of DnaA mutants defective in ATP binding and ATP-specific oligomerization. However, despite their functional equivalency, orisomes assembled on oriC(allADP) were unable to trigger chromosome replication at the correct cell cycle time and displayed a hyper-initiation phenotype. Here we present a new perspective on DnaA-ATP, and suggest that in E. coli, DnaA-ATP is not required for mechanical functions, but rather is needed for site recognition and occupation, so that initiation timing is coupled to DnaA-ATP levels. We also discuss how other bacterial types may utilize DnaA-ATP and DnaA-ADP, and whether the high diversity of replication origins in the bacterial world reflects different regulatory strategies for how DnaA-ATP is used to control orisome assembly.en_US
dc.description.sponsorshipThe work in our laboratories was supported by a Public Health Service grant GM54042. Publication of this article was funded in part by the Open Access Subvention Fund and the Florida Tech Libraries.en_US
dc.publisherFrontiers in Microbiologyen_US
dc.rightsCopyright © 2019 Leonard, Rao, Kadam and Grimwade. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
dc.subjectDNA replicationen_US
dc.subjectreplication originen_US
dc.subjectpre-replication complexesen_US
dc.subjectDNA binding proteinsen_US
dc.subjectcell cycleen_US
dc.titleChanging Perspectives on the Role of DnaA-ATP in Orisome Function and Timing Regulationen_US

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