The phosphoproteomics study of Chk1 and ATR inhibitors regulation on cells

Ataxia Telangiectasia and Rad3-related (ATR) and Checkpoint Kinase 1 (Chk1) are crucial kinases in the DNA Damage Response (DDR) pathway. While the roles of ATR and Chk1 within the DDR are well-established, their roles in mitosis are not fully understood. Here, we describe that the ATR-Chk1 pathway is rewired in mitosis to promote full CDK1 activity, a stark contrast to their role in interphase to inhibit CDK1 following DNA damage. We use mass spectrometry validated the phosphorylation changes after the treatment of ATR and Chk1 inhibitors and confirmed in vitro that Chk1 inhibits residual activity of PKMYT1 (Myt1) via direct phosphorylation at Serine 143.