In vitro ADP-ribosylation of chromosomal proteins of the brain of developing rats

Abstract

In vitro ADP-ribosylation of chromosomal protein and its modulation by spermine, 3-aminobenzamide (3-AB) and benzamide were studied by incubating the nuclei of cerebral hemisphere of 3-, 14- and 30-day old rats with ³²P-NAD⁺. Histones get ADP-ribosylated more than the non-histone chromosomal (NHC) protein. H1 is the major target for ADP-ribosylation. Among the nucleosomal histones, H2B is ADP-ribosylated most. The other core histones also get ADP-ribosylated to a lesser extent. ADP-ribosylation of both histones and NHC proteins decreases during development. Spermine stimulates, whereas 3-AB and benzamide inhibit, ³²P-ADP-ribose incorporation into histones and NHC proteins. These effects decrease with development. Mild digestion of chromatin by micrococcal nuclease (MNase), EcoRI, and AluI prior to ADP-ribosylation stimulates incorporation of ³²P-ADP-ribose. The degree of stimulation decreases as development proceeds. Such alterations indicate progressive condensation of chromatin with development.