Ubinuclein 1 (UBN1) is a ubiquitously expressed evolutionarily conserved protein which binds to proliferation-promoting genes that are repressed by formation of senescence-associated heterochromatin foci (SAHF). Ubinuclein 1 associates with various transcription factors and with histone methyltransferase activity, is indispensable for SAHF formation and appears to be a regulator of senescence. Although in most cells ubinuclein is localized to the nucleus, in cells forming tight junctions it is recruited to the cell adhesion complexes, dependently on the cell density.