Extraction of DNA-binding proteins from cryogenically preserved cells.

We demonstrate that DNA-binding protein extracts can be effectively prepared directly from tissue culture cells preserved under liquid nitrogen without returning the cells to culture. We prepared DNA-binding protein extracts directly upon thawing of T47D, Jurkat and CAC-L153S cell 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 tumor virus transcription in these extracts is indistinguishable from binding activity in similar extracts prepared from cells maintained in culture.