Phosphoproteomics Analysis Reveals a Potential Role of CHK1 in Regulation of Innate Immunity through IRF3

Inhibitors of checkpoint kinase 1 (CHK1), a central component of DNA damage and cell cycle checkpoint response, represent a promising new cancer therapy, but the global cellular functions they regulate through phosphorylation are poorly understood. To elucidate the CHK1-regulated phosphorylation network, we performed a global quantitative phosphoproteomics analysis, which revealed 142 phosphosites whose phosphorylation levels were significantly different following treatment with the CHK1 inhibitor SCH 900776. Bioinformatics analysis identified phosphoproteins that function in ATR–CHK1 signaling, DNA replication, and DNA repair. Furthermore, IRF3 phosphorylation at S173 and S175 was significantly reduced following treatment with SCH 900776. Our findings indicate that the CHK1-dependent regulation of IRF3 phosphorylation at S173 and S175 may play a role in the induction of innate immune response after replication stress or DNA damage, which suggests a potential function of CHK1 in the innate immune response. Data are available via ProteomeXchange with identifier PXD015125.