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. Contrary to its human counterpart, the 9-1-1 complex, the checkpoint clamp complex shows no detectable exonuclease activity. 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. Interacts with the DNA polymerase zeta subunit REV7. 2 RAD17 subunits form also a hetero trimer with one MEC3 subunit. Present with 189 molecules/cell in log phase SD medium. Belongs to the rad1 family.