Genome integrity in eukaryotes depends on licensing mechanisms that prevent 
loading of the minichromosome maintenance complex (MCM2-7) onto replicated DNA 
during S phase. Although the principle of licensing appears to be conserved 
across all eukaryotes, the mechanisms that control it vary, and it is not clear 
how licensing is regulated in plants. In this work, we demonstrate that subunits 
of the MCM2-7 complex are coordinately expressed during Arabidopsis (Arabidopsis 
thaliana) development and are abundant in proliferating and endocycling tissues, 
indicative of a role in DNA replication. We show that endogenous MCM5 and MCM7 
proteins are localized in the nucleus during G1, S, and G2 phases of the cell 
cycle and are released into the cytoplasmic compartment during mitosis. We also 
show that MCM5 and MCM7 are topologically constrained on DNA and that the MCM 
complex is stable under high-salt conditions. Our results are consistent with a 
conserved replicative helicase function for the MCM complex in plants but not 
with the idea that plants resemble budding yeast by actively exporting the MCM 
complex from the nucleus to prevent unauthorized origin licensing and 
rereplication during S phase. Instead, our data show that, like other higher 
eukaryotes, the MCM complex in plants remains in the nucleus throughout most of 
the cell cycle and is only dispersed in mitotic cells.