Crosstalk between BRCA-Fanconi anemia and mismatch repair pathways prevents MSH2-dependent aberrant DNA damage...

Area of Science:

• DNA repair mechanisms
• Cellular response to DNA damage
• Molecular biology

Background:

• The BRCA-Fanconi anemia (FA) and mismatch repair (MMR) pathways are crucial for DNA integrity.
• Interactions between BRCA-FA proteins (e.g., FANCJ, BRCA1, FANCD2) and MMR factors (e.g., MLH1) are known but functionally unclear.
• The MMR pathway is not essential for survival against DNA interstrand crosslinks (ICLs).

Purpose of the Study:

• To investigate the functional significance of crosstalk between the BRCA-FA and MMR pathways in response to ICLs.
• To test the hypothesis that MMR proteins can impair ICL repair when BRCA-FA pathway crosstalk is compromised.

Main Methods:

• Utilized cell lines with specific genetic deficiencies in BRCA-FA and MMR pathway components.
• Employed gene depletion techniques (e.g., MSH2 depletion) to assess effects on ICL sensitivity.
• Investigated DNA damage response, cell cycle progression, and resistance mechanisms.

Main Results:

• Depletion of MSH2 suppressed ICL sensitivity in cells lacking the FANCJ-MLH1 interaction.
• MSH2 depletion restored cell cycle progression and promoted ICL resistance via a Rad18-dependent pathway.
• MSH2 depletion also rescued ICL sensitivity in BRCA1- or FANCD2-deficient cells, but not FANCA-deficient cells.
• Rescue by MSH2 loss was confirmed in primary mouse cells.

Conclusions:

• Regulation of the MSH2-dependent DNA damage response is critical for the functional importance of BRCA-FA and MMR pathway interactions.
• MSH2 plays a key role in potentially detrimental MMR pathway activity during ICL repair when BRCA-FA crosstalk is absent.