Details

Autor(en) / Beteiligte

• Lin, Fang-Tsyr
• MacDougald, Ormond A.
• Diehl, Anna Mae
• Lane, M. Daniel

Titel

A 30-kDa Alternative Translation Product of the CCAAT/Enhancer Binding Protein α Message: Transcriptional Activator Lacking Antimitotic Activity

Ist Teil von

• Proceedings of the National Academy of Sciences - PNAS, 1993-10, Vol.90 (20), p.9606-9610

Ort / Verlag

Washington, DC: National Academy of Sciences of the United States of America

Erscheinungsjahr

1993

Link zum Volltext

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Full-length (42 kDa) CCAAT/enhancer binding protein α (C/EBPα) (p42) has been implicated in the transcriptional activation of adipocyte genes including the 422(aP2) and C/EBPα genes during differentiation of 3T3-L1 preadipocytes. We have identified a 30-kDa isoform (p30) of C/EBPα that is expressed by 3T3-L1 adipocytes, mouse adipose tissue, and rat liver. In vitro translation of wild-type C/EBPα mRNA or transient transfection with a wild-type C/EBPα vector gave rise to similar levels of p42 and p30. Mutational analysis revealed that p30 is an alternative translation product initiated at the third in-frame methionine codon of the C/EBPα message. p30C/EBPαbinds to the C/EBP sites within and activates reporter gene expression driven by the 422(aP2) and C/EBPα gene promoters. Although transfection of 3T3-L1 preadipocytes with a strong p30C/EBPαexpression vector is insufficient to induce differentiation, this vector advances the differentiation program. Unlike p42C/EBPα, which inhibits cell proliferation, p30C/EBPαis not antimitotic. Thus, the N-terminal 12-kDa segment of full-length C/EBPα contains an amino acid sequence necessary for antimitotic activity. During differentiation of 3T3-L1 preadipocytes and during hepatocyte development, the cellular p42C/EBPα/p30C/EBPαratio changes, raising the possibility of a regulatory role.