Effect of inhibitors of protein phosphatase 1 and 2A on erythroid colony formation: an investigation of the specificities of inhibitors

To investigate the possible involvement of protein phosphatase (PP)1 and PP 2A in the process of erythropoiesis, we assessed the effect of PP1 and PP2A inhibitors on erythroid colony formation using an in vitro colony formatio n assay. Okadaic acid (OKA), calyculin A (Cal-A) and tautomycin suppressed colony formation but 1-nor-okadaone did not. These results suggest that PP1 and PP2A both play an important role in erythropoiesis. Furthermore, highe r concentrations of tautomycin were needed to suppress colony formation com pared to concentrations of OKA and Gal-A. The target enzyme of inhibitors i n erythropoiesis may be PP2A.