Sequences in the (A)gamma-delta intergenic region are not required for stage-specific regulation of the human beta-globin gene locus.
The human beta-globin locus has been extensively studied as a model of tissue and developmental stage-specific gene expression. Structural mapping of naturally occurring mutations, including transfection and transgenic studies, and the recent finding of intergenic transcripts have suggested that there are cis-acting sequence elements in the (A)gamma-delta intergenic region involved in regulating gamma- and beta-globin gene expression. To determine whether previously identified sequences in the (A)gamma-delta intergenic region are required for appropriate developmental expression of the human beta-globin gene cluster, transgenic mice were generated by transfer of yeast artificial chromosomes containing the entire human beta-globin locus. Three different deletions of the (A)gamma-delta intergenic region were introduced, including (i) deletion of the 750-bp (A)gamma 3' regulatory element ((A)gammae), (ii) deletion of 3.2 kb upstream of the delta-globin gene encompassing pyrimidine-rich sequences and the recently described intergenic transcript initiation site, and (iii) deletion of a 12.5-kb fragment encompassing most of the (A)gamma-delta globin intergenic region. Analysis of multiple transgenic lines carrying these deletion constructs demonstrated that the normal stage-specific sequential expression of the epsilon -, gamma-, and beta-globin genes was preserved, despite deletion of these putative regulatory sequences. These studies suggest that regulatory sequences required for activation and silencing of the human beta-globin gene family during ontogeny reside proximally to the genes and immediately 5' to the human gamma- and beta-globin genes.
Gaensler
Karin M L
KM
Department of Medicine and Howard Hughes Medical Institute, University of California, San Francisco, CA 94143, USA. gaensler@medicine.ucsf.edu
Zhang
Zemin
Z
Lin
Chin
C
Yang
Suya
S
Hardt
Karin
K
Flebbe-Rehwaldt
Linda
L
D000818:Animals; D018244:Chromosomes, Artificial, Yeast / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D005809:Genes, Regulator; D005914:Globins / Q000235:genetics*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D017384:Sequence Deletion
D005914:Globins