Abstract
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.
Highlights
The non-histone chromosomal(NHC) proteins of several human and hamster cell lines as well as humanhamster cell hybrids were investigated b y one- and two-dimensional gel electrophoresis
The above results showed that themajor NHC proteins of the human-hamster hybrids were indistinguishable electrophoretically from those of the parental hamster cell line with the exception of a single protein in one hybrid
The virtual identity of the NHC proteins of the hybrid and CHOcells indicates that these genes werenot expressed in the hybrid cells
Summary
The Chinese hamster cell was ing in Buffer A to remove detergents and resuspended in a solution the prevalent parental ceU in d l these hybrids since human chromo- containing 0.02 M EDTA, 0.08 M NaCI, pH 6.8, for 15 min to extract somes were selectively lost. The swollen cells were pelleted, resuspended in The radioactive samples (specific activity, 1 t,o 5 X 1 0 dpm/pg of Buffer A, and homogenized thoroughly with a motor-driven Teflon protein) were mixedwith 150pg of unlabeled HeLa or CHO proteins pestle homogenizer.The supernatanotf the subsequent centrifugation (prepared by the first method described above) and isoelectric focuscontained the cytoplasmic proteins.
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