Transcriptional regulation of the human 
6 integrin gene by the transcription factor NFI during corneal wound healing
Manon Gaudreault 1,
Francois Vigneault 2,
Marie-Eve Gingras 1,
Steeve Leclerc 1,
Patrick Carrier 3,
Lucie Germain 3,
and
Sylvain L. Guerin 4*
1 CHUL Research Center, Oncology and Molecular Endocrinology Research Center, Quebec, Canada
2 Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States
3 Hopital du Saint-Sacrement, Laboratoire d'Organogenese Experimentale, Quebec, Canada
4 CHUL Research Center, Oncology and Molecular Endocrinology Research Center, Ste-Foy, Canada
* To whom correspondence should be addressed. E-mail: sylvain.guerin{at}crchul.ulaval.ca.
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Abstract |
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Purpose: Wound healing of the corneal epithelium is highly influenced by regulation of integrin genes expression. Recently, we demonstrated that laminin (LM), a major constituent of the ECM, reduces expression of the human 
6 integrin subunit gene by altering the properties of the transcription factor (TF) Sp1. In this work, we identified a target site for the TF nuclear factor I (NFI) on the human 6 gene and characterized its regulatory influence in corneal epithelial cells. Methods: Plasmids bearing the 6 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 6 promoter was identified by DNaseI footprinting. Expression and DNA binding of NFI was monitored by western blot, RT-PCR and electrophoretic mobility shift assays (EMSAs) and its function 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 6 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 6 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 6 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.
Key Words:
integrin, corneal epithelium, corneal wound healing, laminin, promoter, NFI
