User:Spidrak/DNA replication

Replace sections on prokaryotic and eukaryotic initiation with more general overview of each type, and a link to short articles on initiation, to be prepared from notes on references from Mellor.

General initiation Under most circumstances, cells must replicate their genomes once, and only once, per cell division. This is achieved by controlling the steps required to initiate replication. The complex molecular machine that is assembled to initiate replication must be able to bind to the origin of replication, induce melting to make the DNA bases accessible, permit unwinding of the double helix, synthesise [RNA primers|sectionlink] and child DNA strands and tether the [polymerases|DNA_polymerase] to the parent DNA strand.

Initiation is dependent on the sequential association of a number of components which make up this molecular machine. The role of each component in prokaryotes and eukaryotes is shown below. (For a more detailed view of initation control in each group, see [prokaryotic_replication_control] and [eukaryotic_replication_control])

DnaC and Cdc6/Cdt1 are functionally similar, so what is Cdc6's role?

Cdc45 is scaffold factor on which many others assemble.

Phage gene products required for efficient in vitro replication include the DNA polymerase (gp43),’ DNA polymerase accessory proteins (gp44, gp62, and gp45), single-stranded DNA-binding protein (gp32), and the helicase-primase complex (gp41 and gp61) (for review, see Nossal and Alberts, 1983). Recent DNA footprinting (Selick et al., 1987)’ and protein-DNA cross- linking studies (Hockensmith et al., 1987) have provided a first glimpse of the three-dimensional structure of the T4 replication fork. The in vitro T4 system continues to yield important general lessons concerning the process of DNA replication.

Uses host RNA polymerase to synthesise primers direct from promoter at origin between genes 39&43