ATP hydrolysis by ORC catalyzes reiterative Mcm2-7 assembly at a defined origin of replication.
The origin recognition complex (ORC) is a six-subunit, ATP-regulated, DNA binding protein that is required for the formation of the prereplicative complex (pre-RC), an essential replication intermediate formed at each origin of DNA replication. In this study, we investigate the mechanism of ORC function during pre-RC formation and how ATP influences this event. We demonstrate that ATP hydrolysis by ORC requires the coordinate function of the Orc1 and Orc4 subunits. Mutations that eliminate ORC ATP hydrolysis do not support cell viability and show defects in pre-RC formation. Pre-RC formation involves reiterative loading of the putative replicative helicase, Mcm2-7, at the origin. Importantly, preventing ORC ATP hydrolysis inhibits this repeated Mcm2-7 loading. Our findings indicate that ORC is part of a helicase-loading molecular machine that repeatedly assembles Mcm2-7 complexes onto origin DNA and suggest that the assembly of multiple Mcm2-7 complexes plays a critical role in origin function.
Bowers
Jayson L
JL
Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Randell
John C W
JC
Chen
Shuyan
S
Bell
Stephen P
SP
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism*; D000818:Animals; D004247:DNA / Q000378:metabolism; D004265:DNA Helicases / Q000378:metabolism*; D004261:DNA Replication / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D009154:Mutation; D051738:Origin Recognition Complex; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins
D004268:DNA-Binding Proteins; C497214:ORC1 protein, S cerevisiae; C497223:ORC1 protein, human; C497219:ORC4 protein, S cerevisiae; C497228:Orc1 protein, mouse; C497231:Orc4 protein, mouse; D051738:Origin Recognition Complex; D029701:Saccharomyces cerevisiae Proteins; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate; D004247:DNA; D004265:DNA Helicases