Changes in oncogene mRNA expression during human keratinocyte differentiation.
The nuclear proto-oncogenes are involved in transcriptional regulation and control many cell processes. The role of changes in proto-oncogene expression in controlling the balance between proliferation and differentiation was studied in cultured keratinocytes. Normal human keratinocytes were grown in the serum-free medium MCDB153 with an extracellular calcium concentration of 70 microM. After treatment with different differentiation conditions, cellular RNA was size-fractionated on agarose gels and transferred to nylon membranes which were subsequently hybridized with c-myc, c-jun, and H-ras 32P-labelled probes. Relative RNA loading was assessed using probes for beta-actin and ribosomal 18s RNA. Inducing differentiation by increasing the calcium concentration of the medium from 70 microM to 1.5 mM resulted in a marked decrease in c-myc RNA levels to 26% of control levels within 8 h. After 48 h in 1.5 mM calcium, c-myc levels had recovered to approximately 50% of control levels. There was a gradual reduction in c-jun levels to 56% of control levels by 4 days. Treatment with 10 nM TPA, which also induces keratinocyte differentiation, reduced c-myc RNA levels to 70% of control levels during the first 4 h, but thereafter c-myc levels remained approximately constant for a further 20 h. TGF beta (2 ng/ml), which inhibits keratinocyte growth without inducing differentiation, did not alter c-myc RNA levels over a 4-day period. There were no changes in c-myc levels following the addition of retinoic acid and none of the conditions altered H-ras levels.(ABSTRACT TRUNCATED AT 250 WORDS)
Sharpe
G R
GR
University Department of Dermatology, Royal Liverpool University Hospital, UK.
Fisher
C
C
Redfern
C P
CP
D002118:Calcium / Q000494:pharmacology; D002454:Cell Differentiation; D002478:Cells, Cultured; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005786:Gene Expression Regulation; D016758:Genes, jun; D016259:Genes, myc; D011905:Genes, ras; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D011519:Proto-Oncogenes; D012333:RNA, Messenger / Q000032:analysis*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000494:pharmacology
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D004815:Epidermal Growth Factor; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium