Two mechanisms of chromatin compaction.

2 types of chromatin compaction were studied by cytochemical and ultrastructural approach. The 1st type was induced by cultivating transformed cells with dimethylsulfoxide. It caused cell transition into a more differentiated state coupled with the appearance of multiple small chromatin condensates. The 2nd type was induced by nonionic detergent Triton X-100 and/or saline penetration inside the nuclei. It was found to be connected with hypercompaction of chromocenters with their integral areas left unincreased. Both types of chromatin compaction differ in their capacity to induce toluidine blue polymerization on DNA substrate and in stability of DNA towards an early step of acid hydrolysis. The relation of the 2 mechanisms of chromatin compaction to different ways of DNA folding is discussed.