Two Heads Are Better Than One: Regulation Of Dna Replication By Hexameric Helicases

DNA replication is tightly regulated in a cell cycle to ensure the integrity of genomic information during suc- cessive passages. The replication process can be divided into three major steps as follows: the initial assembly of prereplication complex (pre-RC) at the replication origin, the distortion of the origin (or origin melting) for repli- cation initiation, and the elongation phase during DNA synthesis. In this process, long stretches of double- stranded DNA (dsDNA) must be unzipped in a relatively short time window within a cell growth cycle. The daunting task of unzipping is carried out by a class of efficient molecular machines called helicases, which are shown to be ring-shaped oligomers. Here, we will focus on the current understanding of the replicative helicases involved in cellular and viral DNA replication in eukary- otic cells.