Figure 1.

The importance of fork protection in maintaining genome stability: i. Cellular replication forks can stall for a variety of reasons. In certain circumstances, stalled forks may reverse to aid repair or restart. ii. A number of fork protection factors including RAD51 (described in the text) act to protect nascent DNA from over-processing by cellular nucleases (denoted by ‘pacman’ symbols). iii. This allows subsequent fork restart and/or repair by homologous recombination, and prevents genome instability. iv. In the absence of these protective factors, excessive nucleolytic processing of stalled/reversed forks leads to common fragile site and chromosomal instability, or to inappropriate repair giving rise to chromosomal fusions and radial chromosomes, ultimately leading to genomic instability (v).