Potential tumor suppressor. Required for death receptor-dependent apoptosis. Mediates activation of STK3/MST2 and STK4/MST1 during Fas-induced apoptosis by preventing their dephosphorylation. When associated with MOAP1, promotes BAX conformational change and translocation to mitochondrial membranes in response to TNF and TNFSF10 stimulation. Isoform A interacts with CDC20, an activator of the anaphase-promoting complex, APC, resulting in the inhibition of APC activity and mitotic progression. Inhibits proliferation by negatively regulating cell cycle progression at the level of G1/S-phase transition by regulating accumulation of cyclin D1 protein. Isoform C has been shown not to perform these roles, no function has been identified for this isoform. Isoform A disrupts interactions among MDM2, DAXX and USP7, thus contributing to the efficient activation of TP53 by promoting MDM2 self-ubiquitination in cell-cycle checkpoint control in response to DNA damage. Interacts with MAP1S (PubMed:15205320, PubMed:15753381). Interacts with XPA (PubMed:10888881). Binds to the N-terminal of CDC20 during prometaphase (PubMed:14743218). Binds to STK3/MST2 and STK4/MST1 (PubMed:15109305, PubMed:16510573, PubMed:21199877). Recruited to the TNFRSF1A and TNFRSF10A complexes in response to their respective cognate ligand, after internalization (PubMed:15949439). Can self-associate (PubMed:11857081). Part of a complex with MDM2, DAXX, RASSF1 and USP7 (PubMed:18566590). Interacts with ECM2 (By similarity). Interacts with MOAP1 (PubMed:15949439). Interacts with E4F1 (PubMed:14729613). Interacts with RSSF5 and probably associates with HRAS via a RSSF1 isoform A-RSSF5 heterodimer (PubMed:11857081). Interacts (via C-terminus) with DAXX (via N-terminus); the interaction is independent of MDM2 and TP53 (PubMed:18566590). Interacts (via N-terminus) with MDM2 (via C-terminus); the interaction is independent of TP53 (PubMed:18566590). Interacts with RAB39A (By similarity). Interacts with RAB39B; the interaction is weak (By similarity). Interacts (via N-terminus) with DAXX (PubMed:18566590). Interacts with RAB39B; the interaction is strong (By similarity). Does not interact with RAB39A (By similarity). Interacts (via N-terminus) with DAXX. Localizes to cytoplasmic microtubules during interphase, to bipolar centrosomes associated with microtubules during prophase, to spindle fibers and spindle poles at metaphase and anaphase, to the midzone during early telophase, and to the midbody in late telophase in cells. Colocalizes with MDM2 in the nucleus. Predominantly nuclear. Isoform A and isoform C are ubiquitously expressed in all tissues tested, however isoform A is absent in many corresponding cancer cell lines. Isoform B is mainly expressed in hematopoietic cells. Produced by alternative promoter usage. Produced by alternative splicing of isoform D. Produced by alternative splicing of isoform D. Produced by alternative promoter usage. Produced by alternative splicing of isoform D. Produced by alternative splicing of isoform D. Produced by alternative splicing of isoform D. Produced by alternative splicing of isoform C.