Viral and Cellular Genomes Activate Distinct DNA Damage Responses.

Area of Science:

• Molecular Biology
• Virology
• Cellular Biology

Background:

• The MRE11/RAD50/NBS1 (MRN) complex and ATM kinase are crucial for cellular DNA damage response (DDR) to genomic breaks, halting replication.
• Viruses have evolved mechanisms to evade host cell defenses, including DDR pathways.

Purpose of the Study:

• To investigate the role of the MRN-ATM pathway in defending against DNA virus infection, specifically adenovirus.
• To elucidate the distinct mechanisms by which MRN-ATM responds to viral genomes versus chromosomal breaks.

Main Methods:

• Investigated MRN-ATM interactions with adenovirus genomes.
• Analyzed the impact of viral oncoproteins (E1B-55K/E4-ORF3) on MRN-ATM signaling.
• Assessed the role of H2AX in discriminating between self and non-self genomes during DDR.

Main Results:

• MRN binds to adenovirus genomes, initiating a localized ATM response that inhibits viral DNA replication.
• Adenovirus oncoproteins E1B-55K/E4-ORF3 inactivate the MRN-ATM DDR to permit viral replication.
• A separate, MRN-independent ATM DDR targets viral nuclear domains but does not impede viral replication.
• H2AX foci formation distinguishes viral from chromosomal DNA, dictating localized anti-viral or global DDR.

Conclusions:

• The MRN-ATM pathway provides a critical, localized defense against adenovirus DNA replication.
• Viral strategies to inactivate MRN-ATM are essential for successful adenovirus infection.
• H2AX-mediated discrimination of viral genomes allows for targeted antiviral responses, preserving cellular viability.