Expression of H1 histone genes in mouse-human somatic cell hybrids

The synthesis of H1 histones was studied in nine mouse-human somatic cell hybrid clones containing reduced numbers of human chromosomes. The entire human genome could be accounted for karyologically and by the use of functional assays for specific enzyme markers encoded by human chromosomes. Chromatographic resolution and peptide mapping of species-specific H1 histones failed to reveal human H1 histones to a level of about 1% of total in the nine clones. In addition to the species-specific extinction of human H1 histones, effects were seen on the quantity of mouse H1 histone subtypes produced in four of the nine clones. The remaining five clones produced H1 histones qualitatively and quantitatively identical with those of the mouse parent, which was common to all nine clones. The results suggest at least two levels of control for H1 histone gene expression.