ADP‐ribosylation of proteins in brain regions of rats during postnatal development

Post‐translational modifications of chromatin‐bound proteins play an important role in the regulation of eukaryotic gene expression. Processes such as acetylation, methylation, phosphorylation and ADP‐ribosylation may alter the interaction of these proteins with DNA and consequently affect chromatin conformation and the binding of enzymes and other molecules involved in the regulation of gene expression. In the present study the process of ADP‐ribosylation of chromosomal proteins (histone and nonhistone proteins) in some rat brain regions during postnatal development was investigated; also the effect of epidermal growth factor (EGF) on this process in fetal brain slices was studied. It has been found that the process of ADP‐ribosylation of total histones extracted from rat cerebral cortex and cerebellum at 1, 10 and 30 days of age, increases from 1 to 10 days of age (i.e. the period of maximal cell proliferation) and decreases thereafter, while the process of ADP‐ribosylation of nonhistone proteins (NHPs) sharply decreases during the same developmental period. The addition of EGF to fetal brain slices causes a significant increase of ADP‐ribosylation of total histones (particularly of the histone H1 fraction) and also of NHPs and microsomal proteins. This result is in agreement with the effect of EGF as a mitogen factor, previously shown in astroglial cell cultures.