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Glycoconj J (2008) 25:225235 DOI 10.1007/s10719-008-9114-z
Transcriptional regulation of the fucosyltransferase VI gene in hepatocellular carcinoma cells
Koji Higai & Noriko Miyazaki & Yutaro Azuma &
Kojiro Matsumoto
Received: 23 March 2007 /Revised: 6 January 2008 /Accepted: 23 January 2008 / Published online: 15 February 2008 # Springer Science + Business Media, LLC 2008
Abstract The 1,3-fucosyltransferase VI (FUT VI) protein is a key enzyme for synthesis of sialyl Lewis X and Lewis X in epithelial cells. Despite its importance, how FUT VI expression is regulated has not previously been elucidated. In this work, we examined transcriptional regulation of the FUT VI gene in hepatocellular carcinoma HepG2 cells. 5-Rapid amplification of cDNA ends analysis revealed transcription start sites of FUT VI in HepG2 cells at +65 and +278 nucleotides (nt) downstream of the position registered in the Data Base of Human Transcription Start Sites. We determined promoter regions for FUT VI in HepG2 cells using a luciferase reporter gene assay. The promoter activities of constructs located 5-upstream of the transcription start site decreased when the 186 to 156 and 56 to 19 nt regions were deleted. Site-directed mutagenesis of these regions revealed that two hepatocyte nuclear factor-4 (HNF-4) and one octamer binding transcription factor-1 (Oct-1) binding sites are essential for FUT VI transcription. Furthermore, transient over-expression of HNF-4 but not Oct-1 enhanced both FUT VI promoter activities and FUT VI mRNA levels in HuH-7 cells. These results suggest that two defined regions in the 5-flanking region of the FUT VI transcription start site are critical for FUT VI transcription in HepG2 cells.
Keywords Fucosyltransferase VI .
Hepatocyte nuclear factor . HepG2 cells .Transcriptional regulation
Introduction
The glycan sialyl Lewis X (sLeX), or NeuAc2-3Gal1-4 (Fuc1-3)GlcNAc-R, and its stereoisomer sialyl Lewis A (sLeA), or NeuAc2-3Gal1-3(Fuc1-4)GlcNAc-R, serve as ligands for endothelial E-selectin and are involved in the recruitment of leukocytes to sites of inflammation [1]. Cancer cells that express sialyl Lewis antigens on their cell surfaces have also been known to adhere to endothelial E-selectin and are associated with malignancy and metastasis. Two principle mechanisms for tumor-associated alteration of glycans have been proposed, incomplete synthesis and neosynthesis of glycans [2, 3].
Sialyl Lewis antigens are synthesized by 1,3/4-fucosyltransferases (FUT) activity from the precursor NeuAc2-3Gal1-3/4GlcNAc-R, which is synthesized via...