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. 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). Detected in the nucleus upon heterologous expression. Not detected in the cytoplasm. Not detected in the nucleus. Detected in adrenal gland (PubMed:9129147). Up-regulated by retinoids. 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 originally identified as a potential transcription factor, because of the presence of a potential basic motif and leucine-zipper domain, and because isoform 1 is detected in the nucleus upon heterologous expression. However, homology at several typical position for basic or hydrophobic residues is missing. Besides, another publication showed it is important for normal Golgi apparatus structure and function.