Developmental and hormonal regulation of protein H1 degrees in rodents.

The tissue and cellular distribution and regulation of the chromatin protein H1 degrees has been examined in developing and adult mouse and in rat. The protein appears in specific cell types of solid tissues only when the cells have terminated their maturation. This was found for brain, retina, striated and cardiac muscle, and liver. In tissues that depend on hormones for their function and maintenance, the expression of H1 degrees is dependent on the continued presence of the specific maintenance hormone. In regenerating rat liver the amount of H1 degrees decreases to one-third after the onset of DNA synthesis. The possible role of H1 degrees is discussed in light of these results.