Viral interference with DNA repair by targeting of the single-stranded DNA binding protein RPA

Area of Science:

• Molecular Biology
• Virology
• Genomics

Background:

• Genomic integrity relies on accurate DNA repair.
• Defects in DNA repair pathways are implicated in cancer development.
• Viruses can manipulate host cell processes, including DNA damage responses.

Purpose of the Study:

• To elucidate the mechanism by which murine polyomavirus sensitizes cells to DNA damage.
• To identify the viral protein and host factor involved in this process.
• To explore potential therapeutic implications of this viral strategy.

Main Methods:

• Infection of cells with murine polyomavirus.
• Expression of polyomavirus large T antigen (LT) and its origin-binding domain (OBD).
• Genetic analysis involving overexpression and knockdown of replication protein A (RPA).
• Assessment of DNA damage responses, nuclear foci formation, and recruitment of repair proteins (Rad51, Rad9).

Main Results:

• Murine polyomavirus infection and LT expression significantly sensitize cells (100-fold) to UV and etoposide-induced DNA damage.
• LT's origin-binding domain (OBD) binds to replication protein A (RPA), mediating sensitization.
• Overexpression of RPA confers protection, while RPA knockdown mimics the LT sensitization phenotype.
• LT inhibits RPA recruitment to nuclear foci after DNA damage, preventing the assembly of DNA repair complexes like Rad51 and Rad9.
• This leads to impaired homologous recombination repair of double-strand DNA breaks.

Conclusions:

• Murine polyomavirus LT employs a novel mechanism to disrupt DNA repair by interfering with RPA function.
• This viral interference with DNA damage response pathways highlights a vulnerability that could be exploited.
• Targeting the RPA-LT interaction may offer a strategy to overcome therapeutic resistance in cancer cells.