Binding of HMG 17 to mononucleosomes of the avianβ-globin gene cluster in erythroid and non-erythroid cells

The binding of HMG 17 to stripped core mononucleosomes containing DNA from the avian beta-globin gene cluster was examined to determine whether binding in vitro in this developmentally-regulated gene domain was associated with transcriptional activity or DNaseI-sensitivity in intact nuclei. Mononucleosomes were prepared from primitive and definitive stage embryonic red blood cells of chick embryos, adult reticulocytes, adult reticulocytes in which embryonic rho-globin transcription was induced, and adult thymus cells. Preferential binding by HMG 17 to mononucleosomes containing the beta-globin gene cluster was confined to erythroid-derived mononucleosomes that contain the embryonic rho-globin gene, the adult beta-globin gene, and DNA sequences located between these two genes, but not to those that contain the embryonic epsilon-globin gene. Comparison of these results to the known patterns of transcription and DNaseI-sensitivity within the beta-globin gene cluster shows that HMG 17 binding, although tissue-specific, does not correlate directly with either DNaseI-sensitivity or active gene transcription, but is dependent on other factors present in core mononucleosomes from this active gene domain.