Role of erythroid Kruppel-like factor in human gamma- to beta-globin gene switching.
Erythroid Kruppel-like factor (EKLF) is an erythroid-specific transcription factor that contains zinc finger domains similar to the Kruppel protein of Drosophila melanogaster. Previous studies demonstrated that EKLF binds to the CACCC box in the human beta-globin gene promoter and activates transcription. CACCC box mutations that cause severe beta-thalassemias in humans inhibit EKLF binding. Results described in this paper suggest that EKLF functions predominately in adult erythroid tissue. The EKLF gene is expressed at a 3-fold higher level in adult erythroid tissue than in fetal erythroid tissue, and the EKLF protein binds to the human beta-globin promoter 8-fold more efficiently than to the human gamma-globin promoter. Co-transfection experiments in the human fetal-like erythroleukemia cell line K562 demonstrate that over-expression of EKLF activates a beta-globin reporter construct 1000-fold; a linked gamma-globin reporter is activated only 3-fold. Mutation of the beta-globin CACCC box severely inhibits activation. These results demonstrate that EKLF is a developmental stage-enriched protein that preferentially activates human beta-globin gene expression. The data strongly suggest that EKLF is an important factor involved in human gamma- to beta-globin gene switching.
Donze
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Department of Biochemistry and Molecular Genetics, School of Medicine, University of Alabama at Birmingham 35294.
Townes
T M
TM
Bieker
J J
JJ
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000378:metabolism*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000378:metabolism; D005786:Gene Expression Regulation; D005809:Genes, Regulator; D005914:Globins / Q000096:biosynthesis* / Q000235:genetics*; D015186:Hominidae / Q000235:genetics*; D006801:Humans; D007700:Kinetics; D051741:Kruppel-Like Transcription Factors; D008969:Molecular Sequence Data; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis; D012097:Repressor Proteins; D014157:Transcription Factors / Q000378:metabolism*; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C497244:Kr protein, Drosophila; D051741:Kruppel-Like Transcription Factors; D011994:Recombinant Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C080774:erythroid Kruppel-like factor; D005914:Globins