Multifunctional protein that is involved in the regulation of many processes including tumor suppression, apoptosis, cell cycle progression or transcription (PubMed:10400610, PubMed:11360199, PubMed:16341127, PubMed:18439902). Promotes apoptosis by favouring the activation of caspase-9/CASP9 and allowing apoptosome formation (PubMed:18439902). In addition, plays a role in the modulation of histone acetylation and transcription as part of the INHAT (inhibitor of histone acetyltransferases) complex. Inhibits the histone-acetyltranferase activity of EP300/CREBBP (CREB-binding protein) and EP300/CREBBP-associated factor by histone masking (PubMed:11830591). Preferentially binds to unmodified histone H3 and sterically inhibiting its acetylation and phosphorylation leading to cell growth inhibition (PubMed:16341127). Participates in other biochemical processes such as regulation of mRNA nuclear-to-cytoplasmic translocation and stability by its association with ELAVL1 (Hu-antigen R) (PubMed:18180367). Plays a role in E4F1-mediated transcriptional repression as well as inhibition of protein phosphatase 2A (PubMed:15642345, PubMed:17557114). ; (Microbial infection) Plays an essential role in influenza A, B and C viral genome replication (PubMed:30666459, PubMed:32694517, PubMed:33045004, PubMed:33208942). Mechanistically, mediates the assembly of the viral replicase asymmetric dimers composed of PB1, PB2 and PA via its N-terminal region (PubMed:33208942). Also plays an essential role in foamy virus mRNA export from the nucleus (PubMed:21159877).
