Participates in TNF-alpha-induced blockade of glucocorticoid receptor (GR) transactivation at the nuclear receptor coactivator level, upstream and independently of NF-kappa-B. Suppresses both NCOA2- and NCOA3-induced enhancement of GR transactivation (By similarity). Required for histone gene transcription and progression through S phase (By similarity). Required for histone gene transcription and S phase progression (By similarity). Involved in TNF-alpha-induced activation of NF-kappa-B via a TRAF2-dependent pathway. Acts as a downstream mediator for CASP8-induced activation of NF-kappa-B. Required for the activation of CASP8 in FAS-mediated apoptosis. Self-associates. Interacts with NPAT (By similarity). Interacts with SRRT (By similarity). Interacts (via SIM domains) with SUMO1 and SUMO2 (By similarity). Interacts with SP100; may negatively regulate CASP8AP2 export from the nucleus to the cytoplasm (By similarity). Interacts with NCOA2 and NCOA3 (By similarity). Component of the death-inducing signaling complex (DISC) with CASP8, FADD and FAS. Interacts with TRAF2. Exported from the nucleus to the mitochondria upon FAS activation. Highly expressed in heart, brain, thymus, lung, testis and spleen.