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Molecular and Cellular Biology, May 1999, p. 3571-3579, Vol. 19, No. 5
Division of Medical Genetics, University of
Washington, Seattle, Washington
Received 28 September 1998/Returned for modification 19 November
1998/Accepted 23 February 1999
A cDNA encoding a novel Krüppel-type zinc finger protein,
FKLF, was cloned from fetal globin-expressing human fetal erythroid cells. The deduced polypeptide sequence composed of 512 amino acids
revealed that, like Sp1 and EKLF, FKLF has three contiguous zinc
fingers at the near carboxyl-terminal end. A long amino-terminal domain
is characterized by the presence of two acidic and two proline-rich
regions. Reverse transcription (RT)-PCR assays using various cell lines
demonstrated that the FKLF mRNA is expressed predominantly in erythroid
cells. FKLF message is detectable by RT-PCR in fetal liver but not in
adult bone marrow cells. As predicted from its structural features,
FKLF is a transcriptional activator. In luciferase assays FKLF
activated the
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
FKLF, a Novel Krüppel-Like Factor That
Activates Human Embryonic and Fetal
-Like Globin Genes
- and
-globin gene promoters, and, to a much lower
degree, the
-globin promoter. Studies of HS2-
gene reporter
constructs carrying CACCC box deletions revealed that the CACCC box
sequence of the
gene promoter mediates the activation of the
gene by FKLF. Other erythroid promoters (GATA-1, glycophorin B,
ferrochelatase, porphobilinogen deaminase, and 5-aminolevulinate
synthase) containing CACCC elements or GC-rich potential Sp1-binding
sites were activated minimally, if at all, by FKLF, indicating that
FKLF is not a general activator of genes carrying the CACCC motifs.
Transfection of K562 cells with FKLF cDNA enhanced the expression of
the endogenous
- and
-globin genes, suggesting an in vivo role of
FKLF in fetal and embryonic globin gene expression. Our results
indicate that the protein potentially encoded by the FKLF cDNA acts as
a transcriptional activator of embryonic and fetal
-like globin genes.
*
Corresponding author. Mailing address: University of
Washington, Division of Medical Genetics, Box 357720, Seattle, WA
98195. Phone: (206) 543-3526. Fax: (206) 543-3050. E-mail:
gstam{at}u.washington.edu.
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