Adult stage gamma-globin silencing is mediated by a promoter direct repeat element.
The human beta-like globin genes (5'-epsilon-Ggamma-Agamma-delta-beta-3') are temporally expressed in sequential order from the 5' to 3' end of the locus, but the nonadult epsilon- and gamma-globin genes are autonomously silenced in adult erythroid cells. Two cis elements have been proposed to regulate definitive erythroid gamma-globin repression: the DR (direct repeat) and CCTTG elements. Since these two elements partially overlap, and since a well-characterized HPFH point mutation maps to an overlapping nucleotide, it is not clear if both or only one of the two participate in gamma-globin silencing. To evaluate the contribution of these hypothetical silencers to gamma-globin regulation, we generated point mutations that individually disrupted either the single DR or all four CCTTG elements. These two were separately incorporated into human beta-globin yeast artificial chromosomes, which were then used to generate gamma-globin mutant transgenic mice. While DR element mutation led to a dramatic increase in Agamma-globin expression only during definitive erythropoiesis, the CCTTG mutation did not affect adult stage transcription. These results demonstrate that the DR sequence element autonomously mediates definitive stage-specific gamma-globin gene silencing.
Omori
Akane
A
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8577, Japan.
Tanabe
Osamu
O
Engel
James Douglas
JD
Fukamizu
Akiyoshi
A
Tanimoto
Keiji
K
D000818:Animals; D001483:Base Sequence; D018244:Chromosomes, Artificial, Yeast / Q000235:genetics; D041905:Erythroid Cells / Q000378:metabolism; D004920:Erythropoiesis / Q000235:genetics / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D005914:Globins / Q000235:genetics*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D017354:Point Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology*; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics / Q000502:physiology*; D020218:Response Elements / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic / Q000235:genetics / Q000502:physiology
D005914:Globins