Immunoelectron microscopic localization of the p21 protein in HT1080 human fibrosarcoma cell lines with altered N-ras gene expression.

The cellular localization of the p21 protein was studied by immunoelectron microscopy in human fibrosarcoma cells with different N-ras gene expression. The tumorigenic HT1080 cells--expressing equally the normal and mutant N-ras genes--contained the p21 in the plasma membrane, in pinocytotic areas as well as in the intracellular vesicles. The non-tumorigenic revertants--expressing more normal N-ras gene than the mutant one--contained p21 in the plasma membrane, especially at the cell junctions. These results suggest, that the mutant p21 may locate to the membrane areas connected with pino- or endocytotic functions.