Probable tumor suppressor initially identified as a CDK5R1 interactor controlling cell proliferation . Negatively regulates NF-kappa-B-mediated gene transcription through the control of RELA phosphorylation . Also regulates mitotic G2/M transition checkpoint and mitotic G2 DNA damage checkpoint. Through its interaction with CDKN2A/ARF and MDM2 may induce MDM2-dependent p53/TP53 ubiquitination, stabilization and activation in the nucleus, thereby promoting G1 cell cycle arrest and inhibition of cell proliferation . May play a role in the unfolded protein response, mediating the ufmylation of multiple proteins in response to endoplasmic reticulum stress . May also play a role in the rupture of the nuclear envelope during apoptosis . May regulate MAPK14 activity by regulating its dephosphorylation by PPM1D/WIP1