Nucleosomal organization of the rat liver satellite DNA-containing chromatin during aging.

Nucleosomal organization of the satellite DNA-containing chromatin of the liver of young (18 +/- 2 weeks) and old (100 +/- 5 weeks) rats was examined by nucleases and satellite I DNA probe. The satellite DNA-containing chromatin exhibits lower accessibility to endogenous endonucleases in old rats. The nucleosomal repeat length of this chromatin as investigated from digestion with endogenous endonucleases and MNase differs remarkably from bulk chromatin, though it does not alter with age. However, age-dependent loss of satellite DNA is apparent from hybridization results. Furthermore, DNase I analysis of the satellite DNA-containing chromatin at nucleosomal level reveals a relatively loose organization in young rats than old ones. It also shows an altered 10 bp periodicity as compared to bulk chromatin in both ages. These findings establish organizational differences between rat liver bulk and satellite DNA-containing chromatin. They further show that repeat length and altered 10 bp periodicity are similar in young and old, but accessibility to nucleases declines with age.