Component of the checkpoint clamp complex involved in the surveillance mechanism that allows the DNA repair pathways to act to restore the integrity of the DNA prior to DNA synthesis or separation of the replicated chromosomes. Associates with sites of DNA damage and modulates the MEC1 signaling pathway and the activation of RAD53 in response to DNA damage at phase G1. The complex also physically regulates DNA polymerase zeta-dependent mutagenesis by controlling the access of polymerase zeta to damaged DNA. Component of the checkpoint clamp complex composed of DDC1, MEC3 and RAD17. The interaction with MEC3 is performed in a RAD17-dependent manner. The checkpoint clamp complex loads onto DNA in an ATP-dependent manner through its interaction with the RFC-RAD4 checkpoint clamp loader complex. Interacts with the DNA polymerase zeta subunit REV7 and DPB11. Phosphorylated during cell cycle S-phase and in response to DNA damage. This phosphorylation is MEC14 dependent. Also hosphorylated by CDC28. Present with 238 molecules/cell in log phase SD medium. Belongs to the DDC1 family.