ORC1 (origin recognition complex, subunit 1) is one of six subunits that make up the origin of recognition complex (ORC). The ORC serves as a scaffold for proteins involved in the initiation of DNA replication. Very recently, ORC1 has been found to perform a function independent of its role in DNA replication. In a screen using siRNAs for human ORC proteins to assess their roles in centrosome biology, it was found that ORC1 plays a key role in controlling centriole and centrosome copy number in human cells. ORC1 is also known as replication control protein 1, ORC1L, HSORC1, and PARC1.