Cytoskeleton alterations of NIH/3T3 fibroblast monolayers transfected with Haras-activated oncogene were studied by immunofluorescence, immunoelectron microscopy, and immunoelectrophoretic analysis of actin isoforms. Transformation foci were found to consist of cells with a round shape and rare stress fibers that spread sparsely, forming rare focal contacts and fibronexuses. The loss of stress fibers in transformed cells was confirmed by staining with rhodamine-phalloidin and with a fluorescinated anti-non-muscle cell actin antibody. The transformed cells were anchored to the substrate prominently by filaments that contained fibronectin, as showed by immunoelectron microscopy. A down-regulation of α-actin isoform was observed by immunofluorescence and immunoblotting analysis using a specific monoclonal antibody. The diffuse distribution of α-actin, lacking a specific association with stress fibers, challenges the hypothesis of a connection between α-actin down-regulation and stress fiber loss.
ASJC Scopus subject areas
- Cell Biology