Chromatin in the 5' flanking region of the transcriptionally active chicken adult β (β(A) globin genes is hypersensitive to nuclease digestion. When plasmids carrying this gene are combined with histones in the presence of extracts from 9-day-old chicken erythrocyte nuclei, the resultant complex displays hypersensitive behavior in the same region. No such behavior is observed with extracts from cells in which the β(A)-globin gene is not expressed. Partially purified preparations of the factor conferring hypersensitivity bind preferentially to DNA fragments containing the hypersensitive region.
Emerson, B. M., & Felsenfeld, G. (1984). Specific factor conferring nuclease hypersensitivity at the 5’ end of the chicken adult β-globin gene. Proceedings of the National Academy of Sciences of the United States of America, 81(1 I), 95–99. https://doi.org/10.1073/pnas.81.1.95