A new human cellular protein AUP1. III. The intracellular localization of AUP1 protein in different human and rat cell lines

Previously, we cloned a full-length cDNA of human Aup1 and showed that AUP1 may represent a new cellular target for the two adenovirus oncoproteins, E1A Ad5 and E4ORF3. In this study, we generated a polyclonal anti-AUP1 antibody and examined the subcellular localization of AUP1 in MCF7 cells, HeLa cells, H1299 cells, 293 cells, BRK1 cells and transfectants expressing adenoviruse E1 genes. Double staining of AUP1 and various markers for cytoplasmic structures showed that the pattern of AUP1 distribution in the cytoplasm was puctuate and diffuse and without any colocalization with Golgi apparatus or endoplasmic reticulum. Additional studies with ectopically expressed AUP1, fused with red fluorescent protein (RFP) in H1299 and McG7 human cell lines and BRK1 rat cell line, showed cytoplasmic localization of RFP-AUP1. Western blot analysis revealed that AUP1 was expressed at similar levels in all tested cell lines and had the same molecular weight as the rat protein (45 kDa). Taken together, these results suggest that AUP1 is a cytoplasmic protein that is expressed in all cell lines we examined.