Phosphorylation changes induced by cAMP derivatives in the CHO cell and selected mutants

Phosphorylation analysis of CHO mutants selected for unresponsiveness to the Reverse Transformation reaction of cAMP derivatives has been carried out by 2D gel electrophoresis in hopes of finding mutants differing from the wild-type cell in a minimal number of such phosphorylations. Seven differences in protein phosphorylations in the parental CHO cell have been identified as a result of treatment with db-cAMP. db-cAMP-unresponsive mutants of two kinds have been found: One type has lost all seven of the phosphorylation changes induced by db-cAMP in the wild-type cell. The other type which is equally resistant to the Reverse Transformation response differs from the parental cell in only one (or possibly two) phosphorylation(s) involving a 55 000 D protein. This protein may, therefore, be directly related to the events of Reverse Transformation.