Adenylate cyclase activity and the cAMP level are not directly correlated with transformation by avian sarcoma viruses.

The adenylate cyclase activity was measured in chick embryo fibroblasts (CEF) infected with temperature-sensitive mutants (ts) of avian sarcoma virus (ASV). When CEF transformed with a (ts) mutant at 36 degrees C were incubated at the non-permissive temperature (41 degrees C), recovery from the low adenylate cyclase activity detectable in the transformed state was slower than the disappearance of signs of morphological transformation. After a downward shift of the temperature the activity decreased and this change was also slower than the alteration of cell morphology. The affinity of the enzyme system for ATP also changed after, and not during, morphological alteration. No significant difference was observed between the cAMP levels in ASV-transformed and non-infected CEF. These findings are consistent with the idea that adenylate cyclase is not involved in cell transformation and that the change in its activity is secondary to cell transformation.