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KMID : 0620920020340050379
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Experimental & Molecular Medicine
2002 Volume.34 No. 5 p.379 ~ p.384
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C/EBP binding activity to site F of the rat GLUT2 glucose transporter gene promoter is attenuated by c-Jun in vitro
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Yong Ho Ahn/Jae Woo Kim
Yong Ho Ahn
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Abstract
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The expression of the GLUT2 glucose transporter gene in liver is suppressed in cultured hepatoma cell lines and primary cultured hepatocytes. Earlier report showed that CCAAT/enhancer binding protein (C/EBP) regulates the promoter activity of the rat GLUT2 glucose transporter gene in liver cells. C/EBPα and C/EBPβ activated the promoter activity by binding to at least two regions of the promoter and one of the C/EBP binding sites, named as site F, also has the AP-1 binding consensus. In this study, we investigated whether the AP-1 can influence on C/EBP binding to this site. The addition of recombinant c-Jun protein with liver extract caused the attenuation of C/EBP binding to site F with the appearance of a new shifted band. The shifted band was competed out with the addition of unlabeled AP-1 consensus oligonucleotide, indicating that c-Jun also can bind to site F. Another C/EBP site on GLUT2 promoter, site H, did not bind AP-1. Analysis of the DNA-protein complex revealed that C/EBP and c-Jun bind to site F in mutually exclusive manner rather than form heterodimeric complex with each other. From these results, it is suggested that the transcriptional activation of C/EBP may be influenced by c-Jun protein in certain status of the liver cells, such as acute phase response, as well as hepatocarcinogenesis.
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KEYWORD
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C/EBP, c-Jun, DNA-protein binding, GLUT2 promoter, hepatocyte,
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