Phosphorylation of nonhistone chromatin proteins from neuronal and glial nuclei‐enriched fractions of rat brain

A comparative study of histone acetylation in neuronal and glial nuclei enriched rat brain fractions

“…This is different to rat liver where histone deacetylation occurred under the same experimental conditions [ 191. At present it is difficult to give a sufficient explanation for the low deacetylation of chromatin-bound histones in the rat brain nuclear fractions. However, an artificial reduction of deacetylase activity due to the isolation procedure for 'neuronal and 'glial' nuclei is not very likely since transacetylases, RNA polymerases [20], protein kinases [4] and enzymes responsible for nuclear amino acid incorporation [9] are highly active in these nuclear populations. Since no measurable deacetylase activity was found neither in 'neuronal) nor in 'glial' nuclei as early as after 3 min of incubation a loss of deacetylase activity due to the length of the chasing period can be excluded.…”

“…Rat brain nuclei were isolated from female Wistar rats (150-l 70 g body weight) as described elsewhere [9]. Neuronal (N) and glial (G) enriched nuclear fractions were separated from isolated rat brain nuclei 40 by discontinuous sucrose density gradient centrifugation [4,9]. The nuclear fractions obtained corresponded morphologically to those described previously [4,9] and characterized by [5,10,11].…”

“…Neuronal chromatin ternplated transcription is much less restricted than that of oligodendro-and microglia [ 1,2] . These differences in chromatin template restriction are connected with differences in chromatin composition [3,4] and structure [S,lO] and may be related to different enzymatic modifications of chromosomal proteins such as the previously described higher phosphorylation of neuronal nonhistone proteins [4].…”

Comparison of the number of RNA initiation sites in rat brain fractions enriched in neuronal or glial nuclei

“…Neuronal-(N) and glial-(G)enriched nuclear fractions were separated from isolated brain nuclei by discontinuous sucrose density gradient centrifugation [lo] . The nuclear fractions obtained morphologically corresponded to those described previously [7,10] and characterized by [ 11 ,I 21. The neuronal nuclei enriched fraction obtained as regards its composition is in good accordance with zone I and the glial nuclei enriched fraction with zone IV obtained by Austoker et al [l] by means of zonal centrifugation.…”

“…More recent studies on the initiation of RNA synthesis support the view that chromatin proteins are involved in the selection of initiation sites for RNA polymerases [5,6]. Potentially the different rates of phosphorylation [7] and acetylation [8] of chromatinbound neuronal and glial proteins as well as the differences in chromatin composition between both nuclear fractions [7,9] may be involved in the regulation of neuronal and glial transcription.…”