Dictyostelium cells express an aggregative adenylylcyclase (ACA), responsible for oscillatory cAMP signaling, and a spore germination-specific adenylycyclase (ACG), Overexpression of PKA regulatory (R) subunits blocks oscillatory cAMP signaling but increases basal cAMP levels, while neither ACA nor ACG mRNA could be detected, To test whether a novel type of adenylylcyclase (AC) was responsible for cAMP synthesis, dominant-negative PKA-R subunits (PKA-R(M)) and control R-subunits (PKA-R(c)) were overexpressed in ACA null mutants, Both transformations as well as transformation with an unrelated vector, carrying the same NEO(R) selection marker, induced an AC activity in growing cells with the biochemical characteristics of ACG. Similar vectors with a different URA selection marker did not increase AC activity. We conclude that the aminoglycoside phosphotransferase encoded by the very commonly used NEO(R) selection marker induces ectopic ACG; activity in Dictyostelium cells, (C) 1995 Academic Press, Inc.
