Interferon-gamma-dependent stimulation of human involucrin gene expression: STAT1 (signal transduction and activators of transcription 1) protein activates involucrin promoter activity.

ABSTRACT: Involucrin is one of the precursor proteins of the cornified cell envelope of keratinocytes, and is expressed during the later stages of keratinocyte differentiation. Interferon-gamma (IFN-gamma), a pleiotropic cytokine with anti-proliferative and immunomodulatory activities, is also a potent inducer of squamous differentiation. Using cultured normal human keratinocytes (NHK cells) and simian virus 40-transformed human keratinocytes (SVHK cells), we investigated the effects of IFN-gamma on involucrin gene expression. Expression of involucrin was increased by about 3-fold after treating NHK cells with IFN-gamma (100 units/ml). Northern blot analyses revealed that IFN-gamma increased the expression of involucrin mRNA. The fragment +42 to -2463 in the 5'-flanking region of the human involucrin gene was subcloned into a luciferase reporter vector and the construct (p2463Luc) was transfected into SVHK cells. p2463Luc produced a 3-fold increase in luciferase activity after IFN-gamma treatment. Sequence analysis detected two putative IFN-gamma-responsive regions [G1 (positions -883 to -874) and G2 (-784 to -775)]. Deletion analyses of the p2463Luc vector revealed that the G1 region is critical for the IFN-gamma-dependent up-regulation of the involucrin gene. Gel-shift analyses revealed that STAT1 (signal transduction and activators of transcription 1) protein bound to the G1 region and that involucrin promoter activity was augmented by transfection of a STAT1 expression vector in the presence of IFN-gamma. In contrast, transfection of a STAT1 dominant-negative expression vector suppressed the IFN-gamma-dependent up-regulation of involucrin promoter activity. These results indicate that IFN-gamma stimulates expression of the human involucrin gene via the G1 (-883 to -874) region of the involucrin gene promoter.

SUBMITTER: Takahashi H 

PROVIDER: S-EPMC1220701 | biostudies-other | 1999 Dec

REPOSITORIES: biostudies-other