Transcriptional activation of human zeta 2 globin promoter by the alpha globin regulatory element (HS-40): functional role of specific nuclear factor-DNA complexes.

Abstract

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

Distinction between AP1 and NF-E2 factor-binding at specific chromatin regions in mammalian cells

“…At the same time, genomic footprinting analysis indicated that the AP1/NF-E2 motifs within several mammalian erythroid-speci®c regulatory elements including the locus-control-region of the human b globin locus or so-called b-globin-LCR (Figure 1), are occupied in vivo by factors in an erythroid lineage and developmental stage speci®c manner (Reddy and Shen, 1991;Ikuta and Kan, 1991;Zhang et al, 1993). However, due to the multiplicity of factor-recognition of the AP1/NF-E2 motif as mentioned above, it has been di cult to ascertain whether NF-E2, or another factor such as AP1, actually binds at these transcription regulatory elements on native chromatin in vivo.…”

Loading of DNA-Binding Factors to an Erythroid Enhancer

“…Further remodeling and modification of the chromatin structure must occur in erythroid cells, however, since several new HS sites appear, including those at the HS-40 element and the promoter regions of the -and ␣-globin genes (54, 59). These latter sites apparently result from erythroid lineage-specific binding of nuclear factors to the above transcriptional regulatory elements, as demonstrated by previous genomic footprint analysis of 60) and of the ␣-globin upstream promoters (47).HS-40 acts as a classical enhancer in transient transfection assays (44,46,60), and it confers appropriate developmental control of the human -globin promoter activity in transgenic mice (19,23,45,56). In vitro and in vivo binding studies have shown that the HS-40 enhanceosome consists mainly of six DNA sequence motifs that are bound with nuclear factors in an erythroid lineage-specific manner: two NF-E2/AP1 motifs (5Ј-NA and 3Ј-NA), three GATA-1 motifs (b, c, and d), and a GT motif (26,50,60) (Fig.…”

“…These latter sites apparently result from erythroid lineage-specific binding of nuclear factors to the above transcriptional regulatory elements, as demonstrated by previous genomic footprint analysis of 60) and of the ␣-globin upstream promoters (47).…”

“…Further remodeling and modification of the chromatin structure must occur in erythroid cells, however, since several new HS sites appear, including those at the HS-40 element and the promoter regions of the -and ␣-globin genes (54,59). These latter sites apparently result from erythroid lineage-specific binding of nuclear factors to the above transcriptional regulatory elements, as demonstrated by previous genomic footprint analysis of HS-40 (50,60) and of the ␣-globin upstream promoters (47).…”

Regulation of human alpha-globin gene expression and alpha-thalassemia

“…The regulatory element α-MRE behaves as a classical enhancer; its main function in the normal chromosomal environment is to activate and enhance expression from the ζ-globin and the α-globin promoters (Zhang et al, 1993).…”