1. ¹Department of Physiology and Biophysics, Case School of Medicine, Cleveland, Ohio, USA
2. ²Department of Biochemistry, Case School of Medicine, Cleveland, Ohio, USA
3. ³Department of Reproductive Biology, Case School of Medicine, Cleveland, Ohio, USA
4. ⁴Department of Dermatology, Case School of Medicine, Cleveland, Ohio, USA
5. ⁵Department of Oncology, Case School of Medicine, Cleveland, Ohio, USA

Correspondence: Dr Richard L. Eckert, Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108 N. Greene Street, Baltimore, Maryland 21201, USA. E-mail: reckert@umaryland.edu

Received 17 May 2007; Revised 26 June 2007; Accepted 5 July 2007; Published online 20 September 2007.

Abstract

Involucrin is expressed in the differentiated suprabasal epidermal layers, and an AP1 transcription factor-binding site present in the involucrin promoter distal regulatory region is required for this regulation. This site binds Fra-1, but cofactor interaction at this site has not been adequately characterized. We show that Fra-1 and p300 histone acetyltransferase are present at the AP1 site, as detected by chromatin immunoprecipitation. This interaction is functional, as treating p300 expressing keratinocytes with calcium or 12-O-tetradeconylphorbol-13-acetate, results in a synergistic increase in hINV expression, and this enhanced activation can be reproduced by coexpression of Fra-1 and p300. p300 also co-precipitates with Fra-1, but protein fractionation studies suggest that this interaction requires an additional protein. Fra-1 also interacts with other proteins that interact at the AP1-5 site, including JunD, JunB, Sp1, and P/CAF. Contrary to results in some other systems, Fra-1 functions as a positive transcriptional regulator in human keratinocytes. These studies suggest that a large multiprotein complex, which includes Fra-1, p300, P/CAF, junD, junB, and Sp1 acts at the AP1-5 site to produce a synergistic increase in hINV gene expression.