Regulation of KLF5 involves the Sp1 transcription factor in human epithelial cells.
Human Kruppel-like factor 5 (hKLF5) is a transcription factor with a potential tumor suppressor function in prostate and breast cancers. In the majority of cancer samples examined, a significant loss of expression for KLF5 has been detected. Whereas hemizygous deletion appears to be responsible for KLF5's reduced expression in about half of the cases, the mechanism for reduction is unknown in the remaining half; gene promoter methylation does not appear to be involved. In this report, we studied the regulation of KLF5 and cloned and functionally characterized a 1944-bp fragment of the 5'-flanking region of the hKLF5 gene. Several mitogens as well as global demethylation induced the expression of KLF5, implicating multiple factors in the regulation of KLF5. KLF5's promoter lacks a TATA box and has a GC-rich region. Deletion mapping in combination with promoter activity assay showed that multiple cis-elements are involved in the transcriptional regulation of KLF5, some of which may play a repressor role whereas some others play an enhancer role. The Sp1 site between position -239 and -219 is essential for a basal promoter activity. Deletion or mutations of this Sp1 site significantly reduced promoter activity in several epithelial cell lines. Electrophoretic mobility shift assays (EMSAs) revealed that the Sp1 site binds Sp1 protein in nucleic extracts of different cell lines. In addition, overexpression of Sp1 protein transactivates KLF5 promoter activity. These findings suggest that Sp1 is a key transcription factor in KLF5's dynamic transcriptional regulation.
Chen
Ceshi
C
Department of Oncology and Hematology, Winship Cancer Institute, Emory University School of Medicine, 1365-C Clifton Road, Atlanta, GA 30322, USA.
Zhou
Yingfa
Y
Zhou
Zhongmei
Z
Sun
Xiaodong
X
Otto
Kristen B
KB
Uht
Rosalie M
RM
Dong
Jin-Tang
JT
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D045744:Cell Line, Tumor; D003001:Cloning, Molecular; D017124:Conserved Sequence / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D051766:Early Growth Response Protein 1; D024202:Electrophoretic Mobility Shift Assay; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism; D051741:Kruppel-Like Transcription Factors; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008297:Male; D015741:Metribolone / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011471:Prostatic Neoplasms / Q000235:genetics / Q000473:pathology; D011485:Protein Binding; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012377:Rodentia; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014212:Tretinoin / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; C492214:KLF5 protein, human; C118391:Klf5 protein, mouse; C492215:Klf5 protein, rat; D051741:Kruppel-Like Transcription Factors; D009841:Oligonucleotides; D011993:Recombinant Fusion Proteins; D016329:Sp1 Transcription Factor; D015534:Trans-Activators; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D016222:Fibroblast Growth Factor 2; D000804:Angiotensin II; D015741:Metribolone; D014212:Tretinoin; D004815:Epidermal Growth Factor; D008156:Luciferases; D013755:Tetradecanoylphorbol Acetate