Expression of genes coding for non-histone chromosomal proteins in human-Chinese hamster cell hybrids. An electrophoretic analysis.

The non-histone chromosomal (NHC) proteins of several human and hamster cell lines as well as human-hamster cell hybrids were investigated by one- and two-dimensional gel electrophoresis. In each type of human cell, over 90% of the 230 most prominent NHC proteins were indistinguishable electrophoretically from the NHC proteins of the hamster cells. Of the roughly 10% which were distinct, 11 of the proteins may be human-specific, since they were found in each type of human cell examined. The NHC proteins in seven different stable human-hamster cell lines, which, in total, contained markers for 21 of the 24 human chromosomes, were electrophoretically indistinguishable from those of the parental hamster cell line, with the exception of a single protein in one hybrid line. It is concluded that many of the genes coding for the apparently human-specific NHC proteins are not expressed in these hybrid cells. The single exception to this appeared to be a gene coding for a protein of roughly 300,000 daltons. This protein was synthesized in one of the hybrids, as well as in each type of human cell. Since the NHC proteins of the hybrid and hamster cells were virtually identical, there was no evidence for the expression of genes coding for NHC proteins characteristic of the differentiated state of the parental human cells.