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Manon Gaudreault, François Vigneault, Marie-Eve Gingras, Steeve Leclerc, Patrick Carrier, Lucie Germain, Sylvain L. Guérin; Transcriptional Regulation of the Human α6 Integrin Gene by the Transcription Factor NFI during Corneal Wound Healing. Invest. Ophthalmol. Vis. Sci. 2008;49(9):3758-3767. doi: 10.1167/iovs.08-1913.
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purpose. Wound healing of the corneal epithelium is highly influenced by regulation of integrin gene expression. A recent study demonstrated that laminin (LM), a major constituent of the extracellular matrix (ECM), reduces expression of the human α6 integrin subunit gene by altering the properties of the transcription factor (TF) Sp1. In this work, a target site was identified for the TF nuclear factor I (NFI) on the human α6 gene, and its regulatory influence was characterized in corneal epithelial cells.
methods. Plasmids bearing the α6 promoter fused to the CAT gene were transfected into human (HCECs) and rabbit (RCECs) corneal epithelial cells grown on LM. The DNA-binding site for NFI in the α6 promoter was identified by DNase I footprinting. Expression and DNA binding of NFI was monitored by Western blot, RT-PCR, and electrophoretic mobility shift assays (EMSAs), and its function was investigated through RNAi and NFI overexpression assays.
results. All NFI isoforms were found to be expressed in HCECs and RCECs. Transfection analyses revealed that NFI is a repressor of α6 expression in both types of cells. LM increases expression of NFI, whereas inhibition of each NFI isoform increases promoter activity suggesting that NFI is a key repressor of α6 transcription. In addition, the negative influence of NFI appears to be potentiated by the degradation of Sp1 when cells are grown on LM.
conclusions. Repression of α6 expression therefore contributes to the final steps of corneal wound healing by both reducing proliferation and allowing attachment of the epithelium to the basal membrane.
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