The function of ORC3 (origin recognition complex subunit 3, Ensembl gene identifier ENSG00000135336) is as follows. Component of the origin recognition complex (ORC) that binds origins of replication. DNA-binding is ATP-dependent. The specific DNA sequences that define origins of replication have not been identified yet. ORC is required to assemble the pre-replication complex necessary to initiate DNA replication. Binds histone H3 and H4 trimethylation marks H3K9me3, H3K27me3 and H4K20me3. {ECO:0000269|PubMed:22427655, ECO:0000269|PubMed:31160578}.