Methylation of Chromosomal Proteins in Neuronal and Glial Nuclei Purified from Cerebral Hemispheres of Rat During Postnatal Development

Abstract

The process of methylation of chromosomal proteins [histones and nonhistone proteins (NHP)] in neuronal and glial cell nuclei obtained from cerebral hemispheres of rats at 1, 10, and 30 days of age was investigated. Purified neuronal and glial nuclei were incubated in the presence of S-adenosyl[methyl-3H]methionine. Histone and NHPs were extracted and fractionated by polyacrylamide gel electrophoresis. The results obtained indicate remarkable differences in the process of methylation of histones and NHPs between neuronal and glial nuclei, especially during the first period of postnatal development. In both nuclear populations the histone fraction H3 was labeled to a greater degree than the other fractions and showed the major changes during postnatal development. The densitometric and radioactive patterns of NHPs show considerable changes in the two nuclear populations at the various ages examined. The main difference between neuronal and glial nuclei consists in the intense methylation of proteins with a molecular weight of approximately 100,000, which are present in neuronal nuclei and virtually absent in glial ones. The results obtained may be correlated with the different chromatin structures of neuronal and glial nuclei and with the patterns of maturation and differentiation of neuronal and glial cells during postnatal development.

Macromolecular Turnover in Brain during Aging

“…Moreover dif ferent patterns of posttranslational modifi cations of chromosomal proteins in neuronal and glial nuclei, purified from cerebral hemi spheres of rats at various ages after birth, were found. The main differences between neuronal and glial nuclei consisted in: (a) an intense methylation of NHPs with molecular weight of approximately 100,000 daltons, which are present in neuronal and virtually absent in glial nuclei [Serra et al, 1985]; (b) a higher acetylation after birth of low-molecular-weight NHPs in neuronal than in glial nuclei; (c) the appearance of highly phosphorylatcd proteins (70,000-90,000 daltons) at 10 days of age, which are more evident at 30 days and are absent at 1 day [Serra et al, 1986],…”