Normal rat kidney cells infected with a Rous sarcoma virus (strain LA23) were used to study the dynamics of alpha-actinin-containing aggregates in transformed cells. Experiments were performed by microinjecting living cells with iodoacetamidotetramethylrhodamine alpha-actinin and allowing the fluorescent analogue to incorporate into cellular structures. Subsequent time-lapse recording indicated that the alpha-actinin-containing aggregates can undergo rapid formation, movement, and breakdown. In addition, experiments using the photobleaching recovery technique indicated that alpha-actinin molecules associated with the aggregates have a very high rate of exchange, whereas those associated with adhesion plaques in normal cells exchange much more slowly. The dynamic properties of alpha-actinin-containing aggregates may be closely related to the changes in cellular behavior upon oncogenic transformation.

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