Variations in accessibility of DNA during traumatic regeneration by Owenia fusiformis (polychaete annelid).

One of the earliest events observed in the 'dedifferentiation phase' of traumatic regeneration is an in vivo increase in transcription. In order to see whether that increase corresponds to a variation at the level of genetic material, we prepared chromatin from normal and regenerating animals (12 h after amputation) for transcription in vitro by E. coli RNA polymerase. The template activity of regenerating chromatin was 2.1-fold higher than normal under standard conditions and showed an altered response to variation of the ionic strength of the medium. The accessibility of DNA in the chromatin was tested using mild digestion by DNAase II. Almost twice as much DNA was solubilised from regenerating chromatin as from normal chromatin. These data were correlated with morphological changes (decondensation) observed by electron microscopy.