Determination of the chromatin domain structure in arrayed repeat regions: organization of the somatic 5S RNA domain during embryogenesis in Xenopus laevis.

The size of the DNA loop containing the Xenopus laevis somatic 5S RNA gene cluster has been estimated using a simple, precise and sensitive method that we have developed for use on any tandemly arrayed DNA repeat region, and was found to increase during development We have found that after the mid-blastula transition, when transcription is activated in the embryo, a subset of somatic 5S RNA genes becomes specifically associated with the nuclear matrix. This association correlates with the transcriptional activity of the 5S genes.