The essence of replication timing: determinants and significance

In eukaryotic organisms, chromosomal DNA replication initiates at multiple sites on the chromosome at different times, following a temporal replication program. Though it is intriguing that all eukaryotic cells possess a temporal replication program that is conserved from one cell cycle to the next, it is not known whether this program is essential for the replication process per se, what specifies the temporal replication program, or whether there is a causal relationship between replication timing and other nuclear processes such as transcription. Emerging studies suggest that replication timing may indeed precede and dictate other cellular processes involving chromatin. Moreover, a systematic correlation between altered replication timing and cancer development has been observed. These studies suggest that replication timing may be an important feature of genome organization with vital functional significance.