Stalled replication forks: making ends meet for recognition and stabilization.

In bacteria, PriA protein, a conserved DEXH-type DNA helicase, plays a central role in replication restart at stalled replication forks. Its unique DNA-binding property allows it to recognize and stabilize stalled forks and the structures derived from them. Cells must cope with fork stalls caused by various replication stresses to complete replication of the entire genome. Failure of the stalled fork stabilization process and eventual restart could lead to various forms of genomic instability. The low viability of priA null cells indicates a frequent occurrence of fork stall during normal growth that needs to be properly processed. PriA specifically recognizes the 3'-terminus of the nascent leading strand or the invading strand in a displacement (D)-loop by the three-prime terminus binding pocket (TT-pocket) present in its unique DNA binding domain. Elucidation of the structural basis for recognition of arrested forks by PriA should provide useful insight into how stalled forks are recognized in eukaryotes.