Required for normal Golgi structure and for protein transport from the endoplasmic reticulum (ER) through the Golgi apparatus to the cell surface. Interacts with GORASP2 (PubMed:11739401, PubMed:28049725). Interacts with the GTP-bound form of RAB2, but not with other Golgi Rab proteins (PubMed:11739401). Identified in a complex with RAB2 and GORASP2 (PubMed:11739401). The tankyrase-binding motif (also named TBD) is required for interaction with tankyrase TNKS and TNKS2. ADP-ribosylated by tankyrase TNKS and TNKS2. Poly-ADP-ribosylated protein is recognized by RNF146, followed by ubiquitination. Ubiquitinated by RNF146 when poly-ADP-ribosylated, leading to its degradation. Was initially thought to be a potential transcription factor, localized in the nucleus.