Initiation of DNA damage responses through XPG-related nucleases

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• DNA damage triggers a conserved checkpoint response, crucial for genomic stability.
• Single-stranded DNA (ssDNA) coated by replication protein A (RPA) is a key intermediate for checkpoint activation.
• Identifying factors that initiate this response is vital for understanding DNA repair pathways.

Purpose of the Study:

• To identify novel genes involved in initiating DNA damage checkpoint signaling.
• To characterize the role of the XPG-related endonuclease Ast1 in DNA damage response.

Main Methods:

• A genetic screen in fission yeast was performed to identify genes amplifying checkpoint signals.
• Overexpression of candidate genes was tested with a weak allele of chk1.
• The function of the identified gene, Ast1, was further investigated in relation to other nucleases like Exo1 and Rad2.

Main Results:

• Ast1, a novel XPG-related endonuclease, was identified as a factor promoting checkpoint activation.
• Ast1, Exo1, and Rad2 nucleases are recruited to double-strand breaks (DSBs) and promote ssDNA formation for checkpoint activation and repair.
• This XPG-related pathway is distinct from MRN-dependent responses, and these nucleases are critical in MRN mutants.

Conclusions:

• Multiple nucleases, including Ast1, Exo1, and Rad2, collaborate to initiate DNA damage responses.
• This collaborative nuclease activity is essential for DNA repair and cellular fitness, particularly under conditions of DNA damage.
• The findings reveal a distinct pathway for DNA damage response initiation involving XPG-related nucleases.