MODEL OF CONTINUOUS AND DISCONTINUOUS CHROMATIN COMPACTION, RESULTINGFROM POSITION EFFECT VARIEGATION

A position effect variegation model based on statistical distribution of molecules of compactisator-proteins (position effect variegation mo difier genes products) around compactization initiation centers is sug gested. The model is founded on two theses: 1) The centers, consisting of DNA motifs, are present in both euchromatin and heterochromatin; 2 ) the proteins bind to the DNA and to each other acting in synergy. Wh en a definite level of the DNA-protein binding is exceeded heterochrom atic domains are formed. The model explains continuous and discontinuo us compaction as a consequence of the distribution of irregular initia tion centers along the chromosome.