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Eukaryotic replication origins are 'licensed' for replication early in the cell cycle by loading Mcm(2–7) proteins. As chromatin replicates, Mcm(2–7) are removed, thus preventing the origin from firing again. Here we report the purification of the RLF-B component of the licensing system and show that it corresponds to Cdt1. RLF-B/Cdt1 was inhibited by(More)
In order to ensure precise chromosome duplication, eukaryotes "license" their replication origins during late mitosis and early G1 by assembling complexes of Mcm2-7 onto them. Mcm2-7 are essential for DNA replication, but are displaced from origins as they initiate, thus ensuring that no origin fires more than once in a single cell cycle. Here we show that(More)
In late mitosis and G1, Mcm2-7 are assembled onto replication origins to 'license' them for initiation. At other cell cycle stages, licensing is inhibited, thus ensuring that origins fire only once per cell cycle. Three additional factors--the origin recognition complex, Cdc6 and Cdt1--are required for origin licensing. We examine here how licensing is(More)
All living organisms have to protect the integrity of their genomes from a wide range of genotoxic stresses to which they are inevitably exposed. However, understanding of DNA repair in plants lags far behind such knowledge in bacteria, yeast, and mammals, partially as a result of the absence of efficient in vitro systems. Here, we report the experimental(More)
Correct regulation of the replication licensing system ensures that no DNA is rereplicated in a single cell cycle. When the licensing protein Cdt1 is overexpressed in G2 phase of the cell cycle, replication origins are relicensed and the DNA is rereplicated. At the same time, checkpoint pathways are activated that block further cell cycle progression. We(More)
Plants are unique in the obligatory nature of their exposure to sunlight and consequently to ultraviolet (UV) irradiation. However, our understanding of plant DNA repair processes lags far behind the current knowledge of repair mechanisms in microbes, yeast and mammals, especially concerning the universally conserved and versatile dark repair pathway called(More)
During late mitosis and early G1, replication origins are licensed for subsequent replication by loading heterohexamers of the mini-chromosome maintenance proteins (Mcm2-7). To prevent re-replication of DNA, the licensing system is down-regulated at other cell cycle stages. A small protein called geminin plays an important role in this down-regulation by(More)
All organisms need to ensure that no DNA segments are rereplicated in a single cell cycle. Eukaryotes achieve this through a process called origin licensing, which involves tight spatiotemporal control of the assembly of prereplicative complexes (pre-RCs) onto chromatin. Cdt1 is a key component and crucial regulator of pre-RC assembly. In higher eukaryotes,(More)
During late mitosis and early interphase, origins of replication become "licensed" for DNA replication by loading Mcm2-7 complexes. Mcm2-7 complexes are removed from origins as replication forks initiate replication, thus preventing rereplication of DNA in a single cell cycle. Premature origin licensing is prevented in metaphase by the action of geminin,(More)
In late mitosis and G1, a complex of the essential initiation proteins Mcm2–7 are assembled onto replication origins to 'license' them for initiation. At other times licensing is inhibited by cyclin-dependent kinases (CDKs) and geminin, thus ensuring that origins fire only once per cell cycle. Here we show that, paradoxically, CDKs are also required to(More)