May be required for replication-independent chromatin assembly. Component of the HIRA complex made of UBN1, UBN2, ASF1A, CABIN1 and HIRA (PubMed:25086063, PubMed:25600486). Interacts with HIRA (PubMed:25086063). Localized at rDNA loci in the nucleolus. No visible phenotype. Belongs to the ubinuclein family.