Ehrlich ascites cell (EAC) chalone assay using purified calf thymus-DNA polymerase alpha

A relatively rapid chalone assay using inhibition of purified calf thymus DNA polymerase alpha by Ehrlich Ascites Cell (EAC) chalone has been performed. The DNA polymerase alpha was inhibited in a concentration-related fashion by partially purified EAC chalone ranging from 10 to 200 micrograms/ml. Spermidine was also tested since there has been some suggestion that chalone may be spermidine; we found no effect of spermidine at 170 and 230 microM, but marked inhibition at 33 mM. This assay should facilitate chalone purification, since chalone appears to non-specifically inhibit DNA polymerase alpha.