Acts as a novel regulator of senescence. Involved in the formation of senescence-associated heterochromatin foci (SAHF), which represses expression of proliferation-promoting genes. Binds to proliferation-promoting genes. May be required for replication- independent chromatin assembly. {ECO:0000269|PubMed:14718166, ECO:0000269|PubMed:19029251}. This is the function of UBN1 (ubinuclein 1, ENSG00000118900).