Expression of the transformation-sensitive protein "cyclin" in normal human epidermal basal cells and simian virus 40-transformed keratinocytes.

Abstract

A cell population highly enriched in human epidermal basal cells was obtained and characterized by using antibodies specific for various cell types in the epidermis. Quantitative 2-dimensional gel electrophoretic analysis (isoelectric focusing) of [35S]Met-labeled polypeptides from basal cells and SV-40-transformed keratinocytes showed that the basal cells synthesize very low amounts (< 0.02% of the total protein) of the nuclear, transformation-sensitive protein cyclin as compared to the transformed cells, which synthesize this protein constitutively (0.15% of the total protein). Very low levels of cyclin were observed in total human epidermis, and preliminary studies of 2, basaliomas show a significant synthesis of this protein in these tumors. Immunofluorescence studies using antibodies to proliferating cell nuclear antigen that immunoprecipitate cyclin confirmed the above observations at least in the case of the culture cells. Cyclin may be a central component of the pathway(s) that controls cell proliferation. [This research may be applied to the study of molecular mechanisms underlying malignant transformation.].