FOXP1 phosphorylation antagonizes its O-GlcNAcylation in regulating ATR activation in response to replication stress

Area of Science:

• Molecular Biology
• Cellular Biology
• Cancer Research

Background:

• ATR signaling is vital for sensing and responding to replication stress, ensuring cellular function and survival.
• ATR activation is a tightly regulated process, essential for maintaining genomic stability.

Purpose of the Study:

• To identify novel regulators of ATR activation.
• To elucidate the mechanism by which FOXP1 coordinates ATR activation.
• To investigate the role of FOXP1 modifications in ATR signaling and their relevance in cancer.

Main Methods:

• Identification of FOXP1 as a binding partner for ATR-ATRIP complexes.
• Biochemical assays to demonstrate FOXP1's scaffold function in ATR activation.
• Analysis of FOXP1 O-GlcNAcylation and CHK1-mediated phosphorylation.
• Characterization of pathogenic FOXP1 mutants in tumor tissues.

Main Results:

• FOXP1 functions as a scaffold protein, directly binding RPA-ssDNA and ATR-ATRIP to facilitate ATR recruitment and activation.
• FOXP1 O-GlcNAcylation represses its interaction with ATR; CHK1-mediated phosphorylation inhibits O-GlcNAcylation upon replication stress.
• Pathogenic FOXP1 mutants exhibit compromised ATR activation and impaired replication fork stability, correlating with tumor tissues.

Conclusions:

• FOXP1 plays a critical, non-transcriptional role in coordinating ATR activation during replication stress.
• A regulatory loop involving FOXP1 O-GlcNAcylation and CHK1 phosphorylation fine-tunes ATR signaling.
• FOXP1 represents a potential therapeutic target in tumors with defective ATR activation and FOXP1 mutations.