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Molecular and Cellular Biology, October 1999, p. 7181-7190, Vol. 19, No. 10
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

C/EBPbeta Modulates the Early Events of Keratinocyte Differentiation Involving Growth Arrest and Keratin 1 and Keratin 10 Expression

Songyun Zhu,1 Hye-Sun Oh,1,dagger Minsub Shim,1 Esta Sterneck,2,Dagger Peter F. Johnson,2 and Robert C. Smart1,*

Molecular and Cellular Toxicology, Department of Toxicology, North Carolina State University, Raleigh, North Carolina 27695-7633,1 and Eukaryotic Transcriptional Regulation Group, ABL-Basic Research Program, National Cancer Institute, Frederick Cancer Research and Development Center, Frederick, Maryland 21702-12012

Received 10 February 1999/Returned for modification 19 March 1999/Accepted 30 June 1999

The epidermis is a stratified squamous epithelium composed primarily of keratinocytes that become postmitotic and undergo sequential changes in gene expression during terminal differentiation. The expression of the transcription factor CCAAT/enhancer binding protein beta  (C/EBPbeta ) within mouse epidermis and primary keratinocytes has recently been described; however, the function of C/EBPbeta within the epidermal keratinocyte is unknown. We report here that transient transfection of mouse primary keratinocytes with a C/EBP-responsive promoter-reporter construct resulted in a sevenfold increase in luciferase activity when keratinocytes were switched to culture conditions that induce growth arrest and differentiation. Forced expression of C/EBPbeta in BALB/MK2 keratinocytes inhibited growth, induced morphological changes consistent with a more differentiated phenotype, and upregulated two early markers of differentiation, keratin 1 (K1) and keratin 10 (K10) but had a minimal effect on the expression of late-stage markers, loricrin and involucrin. Analysis of the epidermis of C/EBPbeta -deficient mice revealed a mild epidermal hyperplasia and decreased expression of K1 and K10 but not of involucrin and loricrin. C/EBPbeta -deficient primary keratinocytes were partially resistant to calcium-induced growth arrest. Analysis of terminally differentiated spontaneously detached keratinocytes or those induced to differentiate by suspension culture revealed that C/EBPbeta -deficient keratinocytes displayed striking decreases in K1 and K10, while expression of later-stage markers was only minimally altered. Our results demonstrate that C/EBPbeta plays an important role in the early events of stratified squamous differentiation in keratinocytes involving growth arrest and K1 and K10 expression.


* Corresponding author. Mailing address: Molecular and Cellular Toxicology, Department of Toxicology, North Carolina State University, Raleigh, NC 27695-7633. Phone: (919) 515-7245. Fax: (919) 515-7169. E-mail: rcsmart{at}unity.ncsu.edu.

dagger Present address: Cutaneous Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02115.

Dagger Present address: Molecular Mechanisms in Development Group, Basic Research Laboratory, Division of Basic Sciences, National Cancer Institute, Frederick Cancer Research and Development Center, Frederick, MD 21702-1201.


Molecular and Cellular Biology, October 1999, p. 7181-7190, Vol. 19, No. 10
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.



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