Polymerase Eta Recruits FANCD2 to Common Fragile Sites to Maintain Genome Stability

Area of Science:

• Molecular Biology
• Genetics
• DNA Replication

Background:

• Replicative DNA polymerases struggle with repetitive DNA sequences, necessitating translesion polymerases.
• Polymerase Eta (pol eta) is vital for replication at common fragile sites (CFS), but its mechanism remains unclear.
• The roles of pol eta's non-catalytic domains (UBZ, PIP, F1) in replication stress and CFS are unknown.

Purpose of the Study:

• To elucidate the mechanistic role of pol eta's non-catalytic domains in managing replication stress at CFS.
• To investigate the functional importance of the PIP and UBZ domains of pol eta in cellular replication.
• To understand how pol eta interacts with FANCD2 in preventing genomic instability.

Main Methods:

• Analysis of replication stress, DNA damage, and replication stalling in cells with inactivated pol eta domains (PIP*, UBZ*).
• Assessment of FANCD2 monoubiquitylation and genome-wide recruitment.
• Evaluation of under-replicated DNA, ssDNA gap formation, and cytosolic DNA accumulation.

Main Results:

• The PIP and UBZ domains of pol eta are essential for mitigating replication stress and DNA damage, particularly at CFS.
• Absence of PIP or UBZ domains leads to genome-wide replication stress, stalling, DNA damage, and under-replicated DNA in G2/M.
• Pol eta inactivation causes toxic cytosolic DNA, triggering an innate immune response, and reveals a common pathway with FANCD2.

Conclusions:

• Pol eta's PIP and UBZ domains are critical for maintaining genomic stability, especially at CFS loci.
• Pol eta functions with FANCD2 to prevent replication perturbations and instability at common fragile sites.
• Defects in pol eta domains result in significant genomic instability and an innate immune response due to cytosolic DNA.