Upstream G gamma-globin and downstream beta-globin sequences required for stage-specific expression in transgenic mice.
The human G gamma-globin and beta-globin genes are expressed in erythroid cells at different stages of human development, and previous studies have shown that the two cloned genes are also expressed in a differential stage-specific manner in transgenic mice. The G gamma-globin gene is expressed only in murine embryonic erythroid cells, while the beta-globin gene is active only at the fetal and adult stages. In this study, we analyzed transgenic mice carrying a series of hybrid genes in which different upstream, intragenic, or downstream sequences were contributed by the beta-globin or G gamma-globin gene. We found that hybrid 5'G gamma/3'beta globin genes containing G gamma-globin sequences upstream from the initiation codon were expressed in embryonic erythroid cells at levels similar to those of an intact G gamma-globin transgene. In contrast, beta-globin upstream sequences were insufficient for expression of 5'beta/3'G gamma hybrid globin genes or a beta-globin-metallothionein fusion gene in adult erythroid cells. However, beta-globin downstream sequences, including 212 base pairs of exon III and 1,900 base pairs of 3'-flanking DNA, were able to activate a 5'G gamma/3'beta hybrid globin gene in fetal and adult erythroid cells. These experiments suggest that positive regulatory elements upstream from the G gamma-globin and downstream from the beta-globin gene are involved in the differential expression of the two genes during development.
Trudel
M
M
Department of Genetics and Development, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
Magram
J
J
Bruckner
L
L
Costantini
F
F
D000818:Animals; D004262:DNA Restriction Enzymes; D005786:Gene Expression Regulation; D005796:Genes; D005914:Globins / Q000235:genetics*; D006801:Humans; D008668:Metallothionein / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic
D012333:RNA, Messenger; D005914:Globins; D008668:Metallothionein; D004262:DNA Restriction Enzymes