Characterization of the promoter for the alpha3 integrin gene in various tumor cell lines: roles of the Ets- and Sp-family of transcription factors.
The alpha3beta1 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 alpha3 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 alpha3 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 alpha3 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 alpha3 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 alpha3 integrin gene expression and that the contribution of each element depends on the type of tumor cells.
Katabami
Kouji
K
Department of Microbiology, Hoshi University School of Pharmacy and Pharmaceutical Sciences, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan. tsuji@hoshi.ne.jp
Kato
Takumi
T
Sano
Rikio
R
Ogura
Masaharu
M
Mizuno
Hiromi
H
Itoh
Saotomo
S
Tsuji
Tsutomu
T
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015153:Blotting, Western; D045744:Cell Line, Tumor; D024202:Electrophoretic Mobility Shift Assay; D020862:GC Rich Sequence; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D039201:Integrin alpha3beta1 / Q000235:genetics*; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000378:metabolism; D011401:Promoter Regions, Genetic; D050783:Proto-Oncogene Proteins c-ets / Q000502:physiology*; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D051705:Sp3 Transcription Factor / Q000502:physiology*; D024363:Transcription Initiation Site; D014158:Transcription, Genetic
D039201:Integrin alpha3beta1; D050783:Proto-Oncogene Proteins c-ets; D051705:Sp3 Transcription Factor; D008156:Luciferases