Involucrin is an important marker of epithelial differentiation which expression is upregulated just after basal cells are pushed into the suprabasal layer in stratified epithelia. Several transcription factors and regulatory elements had been described as responsible for turning, oil the gene. However, it is evident that in basal cell layer, additional mechanisms are involved in keeping the gene silent before the differentiation process starts. In this work, we located a potential transcriptional silencer in a 52 bp sequence whose integrity is necessary for silencing the proximal enhancer promoter element (PEP) in multiplying keratinocytes. Octamer-binding sites were noticed in this fragment and the specific binding of Oct-2 transcription factor was detected. Oct-2 appears to be implicated in all epithelia I-specific repression activity recorded only in keratinocytes and C33-A cell line. Overexpression of Oct-2 repressed the involucrin promoter activity in epithelial cells and in the presence of the silencer element. (C) 2004 Elsevier Inc. All rights reserved.