Restriction endonuclease accessibility of the developmentally regulated goat gamma-, beta C-, and beta A-globin genes in chromatin. Differences in 5' regions which show unusually high sequence homology.

The chromatin structure of the developmentally regulated fetal (gamma), preadult (beta C), and adult (beta A) beta-globin genes of the goat has been investigated using a nuclear restriction enzyme accessibility assay. In fetal liver nuclei only the PvuII site immediately proximal to the gamma-globin gene is available for digestion, while the homologous recognition sequences 5' to beta A and beta C are not accessible. Conversely, that site upstream of the beta C transcription unit is exclusively digested in bone marrow nuclei prepared from animals expressing the juvenile form of the protein. In nonerythropoietic tissue none of the PvuII recognition sequences flanking the three genes are digested using identical reaction conditions. These results are particularly striking since the nucleotide sequence extending for hundreds of bases in either direction from this restriction site is remarkably homologous among the three genes. In addition, we have mapped an endogenous nuclease-hypersensitive site approximately 1150 nucleotides 5' to the gamma-globin gene which is evident only in fetal liver tissue.