[Structural-functional organization of the SV40 virus chromosome. III. Nucleosome organization of free mini-chromosomes]

Micrococcal nuclease digestion and hybridization end labeling procedure have been used for analysis of nucleosomal organization of SV40 minichromosomes. Usual oligonucleosomal pattern containing long oligonucleosomes has been observed after digestion and DNA electrophoresis. All the regions of the minichromosome, including the "regulatory" one, are involved in nucleosome structure, as judged by hybridization analysis. This is valid at least for the major minichromosome fraction. On the other hand, the nucleosome ordering turned out to be higher in certain genome regions, for example around the site where the replication terminates. Data implying the existence of several discrete nucleosome "frames" in this region have been obtained. Possible artefacts due to micrococcal nuclease sequence-specificity are discussed.