Involvement of transcription factor Ets-1 in the expression of the [alpha]3 integrin subunit gene

The [alpha]3[beta]1 integrin is an adhesion receptor for extracellular matrix proteins, and plays crucial roles in cell motility, proliferation, and differentiation. The aberrant expression of this adhesion molecule on tumor cells is frequently associated with their malignant behaviors. We previously reported that the Ets transcription factor-binding consensus sequence 133 bp upstream of the mouse [alpha]3 integrin gene is an important element for its expression in various tumor cell lines. In the present study, we attempted to identify a transcription factor bound to the Ets-consensus sequence, and found that Ets-1 bound to this sequence in an electrophoretic mobility shift assay, chromatin immunoprecipitation assay, and pull-down assay with a tandem repeat of the sequence as adsorbent. We next examined the role of Ets-1 in [alpha]3 integrin gene expression by use of a luciferase assay with a reporter plasmid containing the 5'-flanking region of the [alpha]3 integrin gene. Cotransfection of HEK293T cells with an Ets-1 expression construct and the reporter plasmid increased luciferase activity. By contrast, transfection of HT1080 cells (high [alpha]3 integrin expresser) with a dominant-negative mutant of Ets-1 decreased luciferase activity. Overexpression of Ets-1 in HepG2 hepatocellular carcinoma cells (low [alpha]3 integrin expresser) upregulated [alpha]3 integrin expression as assessed by immunoprecipitation. Finally, the induction of [alpha]3 integrin gene expression in HepG2 cells after transforming growth factor-[beta]1 treatment was abrogated by the dominant-negative mutant of Ets-1. These results suggest that Ets-1 is involved in transcriptional activation of the [alpha]3 integrin gene through its binding to the Ets-consensus sequence at -133 bp. [PUBLICATION ABSTRACT]