NUCLEOSOMES AS TOPOLOGICAL RHEOSTATS

Induction of transcription in eukaryotic promoters is accompanied by r emoval or remodeling of nucleosomes. Given that this process causes re lease of torsional stress, the question is asked relative to its fate and to its effects on local DNA conformation. Is it dispersed by free rotation through surrounding nucleosomes or does it stay locally to be used in the modulation or activation of the transcription machinery? The results of the calculations relative to the onset of writhing sugg est that the free energy made available by removal of nucleosomes is i n the range of values that corresponds to the transition linking diffe rence, thus pointing to a possible regulatory mechanism for the local use of free energy in promoters. Nucleosomal core particles(1) (ncps) (1-3) may form on essentially every biological DNA sequence. Given the ir ubiquity and their topological function(s) during transcription and other genetic processes, knowing the consequences of their complex to pological behavior on the modifications of DNA conformation may help u ntangling the dynamics of the regulatory machinery.