Subcellular distribution of DNA-binding proteins from cultured hamster fibroblasts

The distribution between nuclei and cytoplasm of DNA-binding proteins from growing NIL cells was studied. To obtain the subcellular fractions, cell monolayers or cells previously detached from the culture dish were treated with non-ionic detergent N onidet P-40. Proteins with affinity for DNA were isolated from nuclear or cytoplasmic fractions by chromatography on DNA-cellulose columns and were further analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The results show that P8, one of the major components in the 0.15 M NaC1-eluted proteins, is found predominantly in the cytoplasmic fractions, whereas P6, the other main protein peak in this eluate, is more prominent in the nuclear fraction. Among the other proteins eluted at 0.15 M NaC1 from the DNA-cellulose column, P5 and P5' are detected in both nuclear and cytoplasmic fractions. All the other proteins in the 0.15 M NaC1 eluate are present almost exclusively in the cytoplasmic fraction. On the other hand, most of the proteins with higher affinity for DNA, eluted from the column at 2 M NaC1, are present in the nuclear fraction, although they are also detected in the cytoplasm in amounts similar to those observed in the nuclei.