Non-histone chromosomal proteins from HeLa cells. A survey by high resolution, two-dimensional electrophoresis

Analysis of HeLa non-histone chromosomal protein by two-dimensional polyacrylamide gel electrophoresis has revealed more than 450 components, most of which are rare (less than 10,000 copies/cell) and are not detectable in cytoplasm. Chromatin prepared from nuclei isolated by a nonaqueous technique contains essentially all of the proteins found in chromatin from aqueous nuclei, implying that cytoplasmic contamination is not significant. The complexity of chromatin is comparable to that of cytoplasm (500 proteins detected) and greater than that of nucleoplasm (300 proteins detected). Approximately 60 proteins occur in chromatin, nucleoplasm, and cytoplasm; one of these appears to be actin.