RIF1 promotes replication fork protection and efficient restart to maintain genome stability

Area of Science:

• Molecular Biology
• Genetics
• DNA Replication and Repair

Background:

• Homologous recombination (HR) and Fanconi Anemia (FA) proteins limit nuclease activity at stalled replication forks.
• The mechanisms linking replication fork degradation to genome instability are not fully understood.

Purpose of the Study:

• To investigate the role of RIF1, a non-homologous end joining (NHEJ) factor, in protecting stalled replication forks.
• To elucidate how RIF1 deficiency impacts replication fork stability and genome integrity.

Main Methods:

• Analysis of Rif1 knockout cells.
• Assessment of replication fork degradation using nuclease activity assays.
• Investigation of RIF1 interactions with Protein Phosphatase 1.

Main Results:

• RIF1 is enriched at stalled replication forks.
• Rif1 knockout cells exhibit degradation of reversed forks, dependent on DNA2 nuclease.
• RIF1's protective role is independent of NHEJ but relies on Protein Phosphatase 1 interaction.
• RIF1 deficiency delays fork restart and exposes under-replicated DNA.

Conclusions:

• RIF1 is crucial for protecting replication forks from degradation.
• Unprotected replication forks can cause genome instability even in recombination-proficient cells.
• RIF1's function in fork protection is distinct from its role in NHEJ.