Differential Effect of H1 Variant Overproduction on Gene Expression Is Due to Differences in the Central Globular Domain

The in vivo overproduction of two mouse histone H1 variants in homologous mouse fibroblasts has opposite effects on gene expression. Overproduction of H10 results in repression of transcript levels of all polymerase II genes tested. In contrast, overproduction of H1c results in elevated levels of transcripts. We created a series of chimeric H1 genes in which the regions encoding the three structural domains common to this family of these proteins were systematically switched. Overexpression of these genes in vivo resulted in the accumulation of large amounts of the chimeric H1 in chromatin. Analysis of the effects of overproduction of these proteins revealed that the differential effect of H1 variant overproduction on gene expression is due to differences in the central globular domain.