Activator protein 1 transcription factors are fundamental to v-rasHa-induced changes in gene expression in neoplastic keratinocytes.
The induction of mouse skin papillomas by initiation-promotion protocols is associated with aberrant expression of epithelial markers in the tumor mass. Similarly, initiation of mouse keratinocytes with a retrovirus encoding the v-rasHa gene (v-rasHa keratinocytes) causes characteristic alterations of epidermal gene expression (A. A. Dlugosz et at, Cancer Res., 54: 6413-6420, 1994). Because activator protein 1 (AP-1) proteins are likely targets of Ras activation, we have examined the role of AP-1 factors in v-rasHa keratinocytes. Introduction of v-rasHa into keratinocytes up-regulates c-Fos, deltaFos B, and Fra-1 transcripts and protein levels in nuclear extracts. The expression of Jun proteins is not significantly altered in v-rasHa keratinocytes. Transduction of cells with v-rasHa results in increased AP-1-dependent transcriptional activity, which is also simulated by transfection of keratinocytes with either c-Fos or deltaFos B but not Fra-1, suggesting that the up-regulation of c-Fos and deltaFos B contributes to this effect. To explore the role of AP-1 proteins in regulating keratinocyte markers in v-rasHa keratinocytes, we blocked the binding of AP-1 proteins to DNA by infecting keratinocytes with an adenovirus encoding a dominant-negative Fos mutant (A-FOS). A-FOS replaces endogenous Fos proteins in the formation of heterodimers with Jun family members and thus prevents the AP-1 transcription factor from binding to DNA. In v-rasHa keratinocytes, the A-FOS virus reversed the suppression of keratins 1 and 10 transcripts and protein, which is characteristically seen in tumors and v-rasHa keratinocytes. A-FOS also increased protein levels but reduced transcripts for the late marker, loricrin, a component of the cornified envelope. These findings indicate that AP-1 proteins are involved in the changes in gene expression that define the v-rasHa phenotype in mouse keratinocytes.
Rutberg
S E
SE
Laboratory of Cellular Carcinogenesis and Tumor Promotion, Bethesda, Maryland 20892, USA.
Adams
T L
TL
Glick
A
A
Bonovich
M T
MT
Vinson
C
C
Yuspa
S H
SH
D000818:Animals; D014408:Biomarkers, Tumor / Q000096:biosynthesis / Q000235:genetics; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D018450:Disease Progression; D015972:Gene Expression Regulation, Neoplastic; D011905:Genes, ras / Q000235:genetics*; D005819:Genetic Markers / Q000235:genetics; D015603:Keratinocytes / Q000378:metabolism* / Q000473:pathology / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D016761:Oncogene Proteins v-fos / Q000096:biosynthesis / Q000235:genetics; D010212:Papilloma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D012097:Repressor Proteins / Q000096:biosynthesis / Q000235:genetics; D012878:Skin Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018808:Transcription Factor AP-1 / Q000096:biosynthesis / Q000235:genetics*; D014158:Transcription, Genetic; D015854:Up-Regulation
D014408:Biomarkers, Tumor; D005819:Genetic Markers; D016761:Oncogene Proteins v-fos; D012097:Repressor Proteins; D018808:Transcription Factor AP-1