Phosphorylation and acetylation of nonhistone chromosomal proteins of the brain of rats of various ages and their modulation by calcium and estradiol.

$\text{In}\text{vitro}$ phosphorylation and acetylation of nonhistone chromosomal (NHC) proteins and their modulation by Ca⁺⁺ and estradiol were studied by incubating slices of cerebral cortex of 2-, 15- and 84-week female rats with ³²Pi and ¹⁴C-Na-acetate. Phosphorylation pattern of NHC proteins is unique for each age. Ca⁺⁺ and estradiol stimulate phosphorylation of different NHC proteins which is also age-specific. Acetylation of NHC proteins decreases precipitously with age. No unique NHC protein is acetylated preferentially at any age, nor does Ca⁺⁺ stimulate acetylation. Estradiol, however, stimulates acetylation of a few NHC proteins. It is suggested that phosphorylation of NHC proteins and its modulation by effectors may be more important for gene expression than their acetylation.