The prolactin gene hypersensitive sites are present early in development and are not induced by estrogen administration

We have previously shown that two DNase I-hypersensitive sites are present upstream of the PRL gene in pituitary tumors of Fischer 344 rats. In this paper we present a method for examining hypersensitive sites in nontumorous pituitaries where PRL-producing lactotrophs comprise a small percentage of the total cell population. Using this method we are able to show that DNase I-hypersensitive sites in the PRL gene chromatin remain present even when estrogen is withdrawn from animals and PRL synthesis is markedly decreased. Furthermore, the hypersensitive sites appear before sexual development in female rats, and estrogen administration does not affect the appearance of the sites.     

Mapping of DNase I-hypersensitive sites in the upstream DNA of human embryonic epsilon-globin gene in K562 leukemia cells.

We have mapped the DNase I-hypersensitive sites around the epsilon-globin and c-myc genes in two human leukemia cell lines K562 and HL60. In K562 cells in which the epsilon-globin gene is transcribed, six DNase I-hypersensitive sites are found in 6 kilobases (kb) of upstream flanking DNA; in HL60 cells in which the c-myc gene is expressed, two DNase I-hypersensitive sites are observed in 2 kb of upstream DNA. Neither the inactive epsilon-globin gene in HL60 cells nor the inactive c-myc gene in K562 cells displays such upstream DNase I-hypersensitive sites. Our results are consistent with previous studies that have shown DNase I-hypersensitive sites within 1 kb of the 5' end of other expressed genes. In addition, we have found sites displaying even more DNase I sensitivity further upstream of expressed epsilon-globin and c-myc genes. Among the six DNase I-hypersensitive sites of the expressed epsilon-globin gene in K562 cells, the most sensitive site is located about 6 kb upstream of the epsilon-globin gene. When correlated with the DNA sequence upstream of the epsilon-globin gene, this site was found to correspond to a region that contains a stretch of 28 consecutive Ts, three enhancer core-like sequences, and a stretch of consecutive (C-A)15(T-A)6 alternating purine and pyrimidine bases. These findings suggest the possibility that an enhancer element for epsilon-globin gene expression resides within this DNase I-hypersensitive site.     

Gamma delta beta-thalassemia due to a de novo mutation deleting the 5'' beta-globin gene activation-region hypersensitive sites.

gamma delta beta-Thalassemia is a rare disorder of hemoglobin biosynthesis, characterized molecularly by partial or complete deletions of the beta-globin gene complex of 100 kilobases (kb) or greater. Common to all mutants described has been the deletion of the most-5' sequences of the beta-globin complex. We have used the techniques of pulsed-field gel electrophoresis and polymerase chain reaction to study a patient with a clinical gamma delta beta-thalassemia phenotype. This subject developed a de novo deletion on a maternally inherited beta-globin gene chromosome involving approximately 30 kb of sequences 5' to the epsilon gene; the deletion extends from -9.5 kb to -39 kb 5' of epsilon and includes three of the four DNase I hypersensitive sites (at -10.9 kb, -14.7 kb, and -18 kb 5' of epsilon). The remaining sequences of the beta-globin complex, including the DNase I hypersensitive sites at -6.1 kb and all structural genes in cis to the deletion are physically intact, but presumably nonfunctional, as evidenced by the presence of a beta S-globin gene that is not expressed as a sickle hemoglobin. Deletion of DNase I hypersensitive sites on a previously functional beta-globin gene complex confirms the significance of these sites in regulating globin gene expression.