Roles of fetal G gamma-globin promoter elements and the adult beta-globin 3' enhancer in the stage-specific expression of globin genes.
The human fetal G gamma-globin and adult beta-globin genes are expressed in a tissue- and developmental stage-specific pattern in transgenic mice: the G gamma gene in embryonic cells and the beta gene in fetal and adult erythroid cells. Several of the cis-acting DNA sequences thought to be responsible for these patterns of expression are located 5' to the G gamma-globin gene and 3' to the beta-globin gene. To further define the locations and functional roles of these elements, we examined the effects of 5' truncations on the expression of the G gamma-globin gene, as well as the ability of G gamma-globin upstream sequences to alter the developmental regulation of a beta-globin gene, as well as the ability of G gamma-globin upstream sequences to alter the developmental regulation of a beta-globin gene. We found that sequences between -201 and -136 are essential for expression of the G gamma-globin gene, whereas those upstream of -201 have little effect on the level or tissue or stage specificity of G gamma-globin expression. The G gamma-globin upstream sequences from -201 to -136 were, furthermore, capable of activating a linked beta-globin gene in embryonic blood cells; however, a G gamma-globin fragment from -383 to -206 was similarly active in this assay, and the complete fragment from -383 to -136 was considerably more active than either of the smaller fragments, suggesting the presence of multiple cis-acting elements for embryonic blood cells. Our data also suggested the possibility of a negative regulatory element between -201 and -136. These results are discussed in relation to several DNA elements in the G gamma-globin upstream region, which have been shown to bind nuclear factors in erythroid cells. Finally, we observed that removal of the beta-globin 3'-flanking sequences, including the 3' enhancer, from the G gamma-globin upstream-beta-globin hybrid gene resulted in a 25-fold reduction in expression in embryonic blood cells. This suggests that the beta-globin 3' enhancer is potentially active at the embryonic stage and thus cannot be solely responsible for the fetal or adult specificity of the beta-globin gene.
Perez-Stable
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Department of Genetics and Development, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
Costantini
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D000367:Age Factors; D000818:Animals; D004742:Enhancer Elements, Genetic; D015672:Erythroid Precursor Cells / Q000502:physiology*; D005786:Gene Expression Regulation; D005914:Globins / Q000235:genetics*; D006801:Humans; D008099:Liver / Q000196:embryology / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic / Q000196:embryology; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic
D012333:RNA, Messenger; D005914:Globins