The Replication factor C (RFC) heteropentamer includes RFC1, RFC2, RFC3, RFC4, and RFC5. The RFC heteropentamer is part of the multiprotein DNA replicase that functions to replicate DNA prior to cell division and repair DNA damage. RFC is the clamp loader ATPase associated with the DNA replicase. As the clamp loader, RFC uses ATP to recruit, open, and close the PCNA ring to link it to DNA for replication and repair. RFC4 is the 37 kDa subunit of RFC that is part of the core complex formed with RFC2 and RFC5.