EXTRACTION OF DNA-BINDING PROTEINS FROM CRYOGENICALLY PRESERVED CELLS

We demonstrate that DNA-binding protein extracts can be effectively pr epared directly from tissue culture cells preserved under liquid nitro gen without returning the cells to culture. We prepared DNA-binding pr otein extracts directly upon thawing of T47D, Jurkat and CAC-L153S cel l lines after storage in liquid nitrogen for periods of up to one year . Our results show that DNA binding of a repressor of mouse mammary tu mor virus transcription in these extracts is indistinguishable from bi nding activity in similar extracts prepared from cells maintained in c ulture.