Involved in neurodegeneration. Acts as component of the STAGA transcription coactivator-HAT complex. Mediates the interaction of STAGA complex with the CRX and is involved in CRX-dependent gene activation (By similarity). Necessary for microtubule cytoskeleton stabilization (By similarity). Component of the STAGA transcription coactivator-HAT complex, at least composed of SUPT3H, GCN5L2, TAF5L, TAF6L, SUPT7L, TADA3L, TAD1L, TAF10, TAF12, TRRAP, TAF9 and ATXN7. The STAGA core complex is associated with a subcomplex required for histone deubiquitination composed of ATXN7L3, ENY2 and USP22. Interacts with SORBS1, PSMC1 and CRX. Interacts with TRRAP, GCN5L2 and TAF10 (By similarity). Interacts with alpha tubulin (By similarity). In addition to a diffuse distribution throughout the nucleus, it is associated with the nuclear matrix and the nucleolus. It is able to shuttle between the nucleus and cytoplasm (By similarity). Widely expressed in adult tissues, with the highest expression in heart, brain, liver and kidney. Proteolytically cleaved. Sumoylation has no effect on subcellular location or interaction with components of the STAGA complex. Belongs to the ataxin-7 family.