We studied the functional interaction between human embryonic C2 globin promoter and the a globin regulatory element region. These data suggest that transcriptional activation of human embryonic g2 globin gene and the fetal/adult a globin genes is mediated by erythroid cell-specific and developmental stage-specific nuclear factor-DNA complexes which form at the enhancer (HS-40) and the globin promoters.Similar to those of other vertebrates, the human ,3-and a-like globin gene families are each arranged as gene clusters. The Pi cluster is on chromosome 11, and the a cluster is on chromosome 16 (reviewed in reference 5). Transcriptional activities of genes contained within both clusters are confined in erythroid cells, and they are sequentially turned on and off during development in the order of their physical arrangement in the clusters (reviewed in reference 15). Genetic evidence and direct experimental data suggest that the regulation of each globin gene family is controlled by regulatory elements located many kilobases upstream of each gene cluster (11,12,41). These sequences, referred to as the I locus control region (P-LCR) and the a. globin regulatory element (HS-40), not only act as classical enhancers in transient expression assays (references 21, 22, 28, 35, and 42 and this study) but also confer erythroid lineagespecific and integration site-independent expression of linked promoters in stably transformed cell lines or transgenic mice (11, 12; reviewed in references 7, 25, and 36).Similar to the 1-LCR (8,11,41), the location of ao globin regulatory element was first mapped near one of four erythroid cell-specific, DNase

The 5' DNase I-hypersensitive site 2 (5' is an erythroid-specific enhancer located 11 kilobases (kb) upstream of the human 13-globin gene duster. Presence in cis of 5' HS-2 confers a high level of erythroid cell-speific and developmentally regulated promoter activities of human globin genes in transfected cell cultures and in transgenic mice. Combining the use of the methylation protection assay and polymerase chain reaction, we have studied nuclear factor-DNA interactions of the 5' HS-2 enhancer in vitro and in vivo. protects the NF-E2/AP1 motif from methylation, but the footprints are different. This is most likely due to different protein-DNA contacts of the AP1-DNA complex formed in HeLa extract and the NF-E2-DNA complex in K-562 extract. In vivo methylation protection patterns of this motif parallel those observed in vitro, suggesting that it is also bound by NF-E2 in K-562 cells and by AP1 in HeLa cells. Finally, a GT-I motif binds apparently to one or more similar factors in both types of nuclear extracts, but the in vivo methylation protection patterns are not identical between living HeLa and K-562 cells. These data provide direct evidence that specific nuclear factor-DNA complexes form in vivo at functionally important sequence motifs of the 5' HS-2 enhancer in erythrold cells. The detection of conformationally different nuclear factor-DNA complexes at the same sequence motifs in HeLa and Raji cell lines also raises interesting questions regarding the origin and function of these complexes in nonerythroid cells.In all vertebrates, the a-globin-like and P3-globin-like gene families are transcribed only in erythroid cells, and different globin genes are expressed at different stages ofthe erythroid development (reviewed in ref.

Dimethyl sulfoxide (DMSO) induction of mouse erythroleukemia (MEL) cells represents a well-defined in vitro system of terminal erythroid differentiation. We have studied the molecular mechanisms of transcriptional activation of the mouse 3m globin gene during MEL cell differentiation by analyzing nuclear factor-DNA interactions in vivo at the gene's upstream promoter and a distal enhancer, 5'HS-2. Genomic footprinting data indicate that three motifs, CAC, NF-E2/AP1, and GATA-1, of the 5'HS-2 enhancer are bound with nuclear factors in MEL cells both prior to and after DMSO induction. No obvious conformational change of these nuclear factor-DNA complexes could be detected upon terminal differentiation of MEL cells. On the other hand, DMSO induction of MEL cells leads to the formation of specific nuclear factor-DNA complexes at several transcriptional regulatory elements of the mouse 13'J globin upstream promoter. Our genomic footprinting data have interesting implications with respect to the molecular mechanisms of transcriptional regulation and chromatin change of the mouse 13"O globin gene during erythroid differentiation.

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The purpose of this study is to characterize glutathione S-transferase (GST) gene expression in airway epithelium both in vivo and in vitro. Immunohistochemical staining of nonhuman primate lungs of well-controlled healthy animals reveals the presence of alpha- and pi-class GST isoenzymes in ciliated bronchial epithelium. The stain of mu-GST antibody is either very low or absent in some of these monkey lungs. We observed that primary tracheobronchial epithelial (TBE) cells isolated from human and monkey pulmonary tissues maintain a relatively high level of GST enzymatic activity in culture, compared with various immortalized human TBE cell lines and other nonpulmonary cell lines. Northern blot analysis demonstrated the presence of mu-, pi-, and microsomal-GST messages but not the alpha-class message in cultures of primary TBE cells as well as in various human TBE cell lines. The expression of mu- and pi-class GST genes can be further regulated in culture by various environmental factors; however, most of these regulating factors are associated with TBE cell differentiation in culture. For instance, vitamin A treatment, which was shown to enhance mucous cell differentiation in vitro, stimulated the message levels of mu- and pi-class GST. Furthermore, plating cells on collagen gel substrata, which also enhanced mucous cell differentiation in culture, instead of plastic culture surface, enhanced total GST enzymatic activity by eightfold, and this enhancement is related to an increase in the expression of the pi-class GST gene. These results demonstrated that GST genes are differentially expressed and regulated by various environmental factors in primary TBE cells and various cell lines, and the regulation is correlated to the mucous cell differentiation in culture.