Figure 1.
How can PCNA mutation affect DNA repair but not replication? Top: Schematic of DNA replication and repair sites in vivo. Replication factories processing Okazaki fragments generate high local concentrations of PCNA, not seen at repair sites. Bottom: The Ser228Ile alteration in PCNA destabilises its interaction with PIP-box containing partner proteins, increasing the KD for crucial binding reactions. This will have a greater biological effect when PCNA concentrations are low, i.e., at repair sites. Crystal structure of PCNA and PIP box rendered in Rasmol from 1AXC (www.rcsb.org).