Eukaryotic origins of DNA replication: could you please be more specific?

Initiation of eukaryotic DNA replication commences when the origin recognition complex (ORC) binds to DNA, recruiting helicases, polymerases, and necessary cofactors. While the biochemical mechanism and factors involved in replication initiation appear to be highly conserved, the DNA sequences at which these events take place in different organisms are not. Thus, while ORC appears to bind to specific DNA sequences in budding yeast, there is increasing new evidence that metazoan ORC complexes do not rely on sequence to be directed to origins of replication. Here, we review examples of specific and non-specific initiation, and we consider what, if not DNA sequence, accounts for DNA binding of ORC to defined regions in eukaryotic genomes.