PNNL

Abstract

The nuclear protein c-Jun is a 39 kD sequence specific transcription factor involved in cell proliferation, transformation and differentiation. Two different c-Jun antibodies, SC-45 (Santa Cruz) and Ab-1 (Oncogene), have been widely used to detect the c-Jun protein. The epitope of SC-45 contains Thr 91 and 93 which are phosphorylated by glycogen synthase kinase-3 (GSK-3) and casein kinase-II (CKII) resulting in the inactivation of c-Jun. In this manuscript, we compared the immunoreactivity of these two c-Jun antibodies in normal mouse hepatocytes and hepatic tumors by immunohistochemistry and Western blotting, In dichloroacetate (DCA)-induced tumors, the protein detected by SC-45 was diffusely spread throughout the cytosol, whereas the protein detected by Ab-1 focused around the nuclei. In the liver tissue adjacent to the DCA-induced tumor, SC-45 stained protein in the nuclei while there was no staining in the nuclei with Ab-1. In SCA-treated mice, SC-45 also detected an increased cytosolic expression of protein in cells that surrounded the central vein. This was not detected by Ab-1. On Western blot analysis, the c-Jun immunoreactive protein highly expressed in DCA-induced tumors was 55 kD rather than 39 kD. Interestingly, the apparent concentrations of the proteins detected at 55 kD varies reciprocally in tumor and surrounding normal tissue. SC-45 detected higher amounts of the 55 kD protein in non-tumor tissue, whereas Ab-1 detected higher amounts of the 55 kD protein in tumor tissue