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Characterization of the promoter for the α3 integrin gene in various tumor cell lines: Roles of the Ets‐ and Sp‐family of transcription factors
Author(s) -
Katabami Kouji,
Kato Takumi,
Sano Rikio,
Ogura Masaharu,
Mizuno Hiromi,
Itoh Saotomo,
Tsuji Tsutomu
Publication year - 2005
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.20663
Subject(s) - transcription factor , integrin , integrin, beta 6 , biology , microbiology and biotechnology , laminin , gene isoform , electrophoretic mobility shift assay , promoter , cell adhesion molecule , gene , gene expression , cell adhesion , extracellular matrix , cell culture , cell , genetics
The α3β1 integrin is an adhesion receptor for extracellular matrix proteins, including laminin isoforms, and plays crucial roles in the organization of epithelial and endothelial tissues. The aberrant expression of this adhesion molecule on tumor cells is associated with their invasive and metastatic potentials. In the present study, we analyzed the elements essential for α3 integrin gene expression in various tumor cell lines with different tissue origins by luciferase assay. An approximately 0.3 kb fragment of the 5′‐flanking region of the mouse α3 integrin gene (−260/+84, relative to the major transcription start site) showed strong promoter activity in all six examined tumor cell lines. However, we found that these cell lines could be divided into two groups according to the level of dependency on the putative Ets‐transcription factor binding motif located at −133. This motif was previously shown to be crucial for α3 integrin expression in MKN1 gastric carcinoma cells. The gene expression in one group of cell lines was upregulated mainly by the Ets motif, whereas that in the other group was less dependent on the Ets motif. We then postulated that additional regulatory elements were responsible for the expression of α3 integrin, and found that a GC‐rich motif at −69 was another important element. An electrophoretic mobility shift assay using specific antibodies and a Western blot analysis of nuclear proteins revealed that the Sp3‐transcription factor bound to this GC‐rich motif. These results suggest that the Sp3 and Ets transcription factors cooperatively regulate α3 integrin gene expression and that the contribution of each element depends on the type of tumor cells. J. Cell. Biochem. © 2005 Wiley‐Liss, Inc.