title: Transcription factors C/EBP alpha, C/EBP beta, and CHOP (Gadd153) expressed during the differentiation program of keratinocytes in vitro and in vivo.
abstract: CCAAT-enhancer binding proteins (C/EBP) are basic region/leucine zipper (bZIP) transcription factors selectively expressed during the differentiation of liver, adipose tissue, blood cells, and the endocrine pancreas. Here we show that C/EBP isoforms are differentially expressed in the skin. BALB/MK keratinocytes incubated in 0.12 mM calcium medium undergo a differentiation program featuring growth-arrest at 24-48 h, keratin K10 gene expression beginning at 24 h, and apoptosis commencing at 48 h. Within this framework, western immunoblot analysis and immunohistochemistry reveal that C/EBP alpha increases 5-fold at 1-2 d and remains elevated, C/EBP beta rises 2-fold at 2-4 d and gradually falls, and CHOP rises 9-fold in the first 24 h then returns rapidly to baseline. Several products of alternative translation are observed in BALB/MK cells, i.e., 42 kDa and 30 kDa forms of C/EBP alpha, and 32 kDa and 20 kDa forms of C/EBP beta. By immunohistologic examination of human, rat, and mouse skin, all three transcription factors are highly expressed within epithelial compartments in a spatially restricted distribution. C/EBP alpha is concentrated in the upper epidermis in a predominantly cytoplasmic location within cells, whereas the highest levels of C/EBP beta and CHOP are seen in the mid-epidermis, mainly within nuclei. High levels of C/EBP beta and CHOP (but not C/EBP alpha) are also observed in hair follicles and sebaceous glands. The identity of these factors in the epidermis is confirmed by western immunoblot analyses. In summary, C/EBP are expressed in a differentiation-associated manner in the skin, and may play an important role in regulating one or more aspects of the epidermal differentiation program.
authors.affiliation: Department of Dermatology, Massachusetts General Hospital, Boston 02114, USA.
authors.forename: E V
authors.initials: EV
authors.lastname: Maytin
authors.forename: J F
authors.initials: JF
authors.lastname: Habener
mesh_terms: D000818:Animals; D015153:Blotting, Western; D022762:CCAAT-Enhancer-Binding Proteins; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D000078404:Epidermal Cells; D004817:Epidermis / Q000378:metabolism; D006801:Humans; D015603:Keratinocytes / Q000166:cytology* / Q000378:metabolism*; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D051381:Rats; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; C497249:DDIT3 protein, human; D004268:DNA-Binding Proteins; C497250:Ddit3 protein, mouse; C497251:Ddit3 protein, rat; D009687:Nuclear Proteins; D014157:Transcription Factors; D051742:Transcription Factor CHOP