Required for resumption of chromosome replication after DNA damage, specifically in S phase. Is recruited to chromatin in the presence of RTT109 and RTT101 in response to stalled replication forks and acts as a scaffold during DNA repair. Forms a complex with the cullin-RING ligase (CRL) RTT101(MMS1-MMS22). Interacts with MMS22 and RTT101. Interacts with histone H2A; requires H2A to be phosphorylated (gamma-H2A). Interacts with RAD55. Recruited to chromatin in response to replication fork stalling. Phosphorylated by MEC1. Present with 1380 molecules/cell in log phase SD medium.