IMMUNOGOLD LABELING OF ONCOGENIC AND TUMOR-RELATED PROTEINS

Immunogold labeling electron microscopy technique has been used to stu dy the ultrastructural localization of oncogenic proteins: Mos, Met, S ki, and the tumor-associated protein, Muc1, as well as their relations hip with other tumor-related proteins. By pre- and postembedding immun ogold labeling electron microscopy techniques, we showed that the Mos protein pp39(mos) colocalized with microtubule bundles, suggesting tha t microtubulin or microtubule-associated protein(s) may be the substra te of Mos. Met protein was labeled at the microvilli of the lumen that are formed in cultured T47D cells, implying its potential involvement in lumen formation. Ski localization experiments revealed a unique gl obular structure ''Ski body'' that is present inside the nucleus of in terphase chicken embryo fibroblast infected with Ski cDNA FB29 and FB2 -29. Ski bodies were also found scattered in the cytoplasm of metaphas e FB29 and FB2-29 Ski expressing chicken embryo fibroblasts. In T47D c ells, tumor-associated protein Muc1 was associated with both the plasm a membrane and the membranes of secretory vesicles in the cytoplasm. I n MUC1 infected NIH3T3 cells, however, labeling showed that in additio n to the plasma membrane and the membranes of secretory vesicles, some Mud gold spheres were seen inside the secretory vesicles, suggesting that the subcellular localization of the protein may vary in different cell types. (C) 1995 Wiley-Liss, Inc.