Abstract
Interleukinโ1 receptor antagonist (ILโ1Ra) is involved in many processes, including epidermal inflammation and hyperplasia after irritation or injury. However, the mechanism by which intracellular ILโ1Ra (icILโ1Ra) expression is regulated in mouse keratinocytes has not been reported. We found that the CH72 mouse carcinoma cell line constitutively expresses the icILโ1Ra mRNA. To study the transcriptional factors responsible for the constitutive expression of icILโ1Ra, we functionally characterized 4.5 kb of the 5โฒ flanking region of the human icILโ1Ra gene in these cells. We first demonstrated that icILโ1Ra expression in these cells was regulated at the level of transcription. Deletion analysis of the promoter showed that regulatory elements for constitutive expression were located โ158 to โ49 bp upstream of the transcription start site for icILโ1Ra. We investigated the cisโ and transโacting factors required for icILโ1Ra expression. An activating proteinโ1 (APโ1) site was identified as the positive regulatory element necessary for the constitutive expression of the icILโ1Ra promoter in CH72 cells. Moreover, electrophoretic mobility shift assay and cotransfection experiments showed that cโjun and cโfos proteins bound to the APโ1 site and functionally transactivated the icILโ1Ra promoter in mouse carcinoma CH72 cells. ยฉ 2002 WileyโLiss, Inc.