NUCLEOSOME POSITIONING AND PERIODICITY OF SATELLITE DNA IN THE LIVER OF AGING RATS - NUCLEOSOME POSITIONING AND PERIODICITY OF SATELLITE DNA

The positioning of nucleosomes has been analysed by comparing the patt ern of cutting sites of a probing reagent on chromatin and naked DNA. For this purpose, high molecular weight DNA and nuclei from the liver of young (18 +/- 2 weeks) and old (100 +/- 5 weeks) Wistar male rats w ere digested with micrococcal nuclease (MNase) and hybridized with P-3 2-labelled rat satellite DNA probe. A comparison of the ladder generat ed by MNase with chromatin and nuclei indicates long range organizatio n of the satellite chromatin fiber with distinct non-random positionin g of nucleosomes. However, the positioning of nucleosomes on satellite DNA does not vary with age. For studying the periodicity and subunit structure of satellite DNA, high molecular weight DNA from the liver o f young and old rats were digested with different restriction enzymes. Surprisingly, no noteworthy age-related change is visible in the peri odicity and subunit structural organization of the satellite DNA. Thes e results suggest that the nucleosome positioning and the periodicity of liver satellite DNA do not vary with age.