Initiation of DNA replication in eukaryotes: questioning the origin.

Although proteins involved in DNA replication in yeast have counterparts in multicellular organisms, the definition of an origin of DNA replication and its control in higher eukaryotes might obey to different rules. Origins of DNA replication that are site-specific have been found, supporting the notion that specific DNA regions are used to initiate DNA synthesis along metazoan chromosomes. However, the notion that specific sequences will define origins is still being debated. The variety and complexity of transcriptional programs that have to be regulated in multicellular organisms may impose a plasticity that would not be compatible with a fixed origin simply defined at the sequence level. Such a plasticity would be essential to developmental programs where the control of DNA replication could be more integrated to the control of gene expression than in unicellular eukaryotes.