Localization and organization of microfilaments and related proteins in normal and virus transformed cells

The localization and organization of actin like microfilaments in normal, SV 40 and adenovirus transformed cells can be determined by the coordinated use of light optical, electron optical and biochemical techniques. In adenovirus type 5 transformed hamster embryo cells, microfilament meshworks appear to be the predominant organizational form of cellular actin, while in normal hamster cells, microfilament bundles are prevalent. Differences between 3T3 and SV 40 transformed 3T3 cells are less apparent and may be related to the packing and intracellular distribution of microfilament bundles. Attempts at relating these ultrastructural changes in transformed cells to the images obtained following reaction with fluorescein labeled myosin fragments and indirect immunofluorescence with smooth muscle myosin antibody are discussed. In several instances the fluorescence microscope images do not correspond to the ultrastructural observations. The results are discussed in terms of the possible relations between alterations in cytoplasmic contractile elements and the abnormal behavior of transformed cells.