title: Characterization of the transcriptional signature of C/EBPbeta isoforms (LAP/LIP) in Hep3B cells: implication of LIP in pro-survival functions.
abstract: OBJECTIVE
  C/EBPbeta is an important mediator of several cellular processes, such as differentiation, proliferation, and survival of hepatic cells. However, a complete catalog of the targets of C/EBPbeta or the mechanism by which this transcription factor regulates certain liver-dependent pathways has not been clearly determined. Two major natural isoforms of this transcription factor exist: the liver-enriched activating protein (LAP) and the liver-enriched inhibitory protein (LIP), a functional LAP antagonist. In this study, we used the opposing transcriptional effects driven by LAP and LIP to determine the genuine C/EBPbeta molecular signature in the Hep3B human hepatoma cell line. We subsequently investigated the role of each of the LAP and LIP isoforms in drug-induced Hep3B cell death.
  
  
  METHODS
  We engineered Hep3B cells with regulated LAP or LIP expression using the Tet-off expression system. The genes that showed inverse regulation by LAP and LIP were identified by cDNA array analysis. The cohort of direct-C/EBPbeta-targets was distinguished from indirect-targets by ChIP-on-chip analysis.
  
  
  RESULTS
  We characterized 676 genes by this approach. Among these genes, 39 are novel direct targets of C/EBPbeta. Eleven of these new direct targets are involved in cell survival, suggesting critical roles for LAP/LIP isoforms in this cellular process. Therefore, we examined the effects of LAP and LIP over-expression on cell survival. We show that LIP promotes survival in staurosporine- or taxol-induced Hep3B cell death.
  
  
  CONCLUSIONS
  Our study provides new molecular and cellular insights into the role of C/EBPbeta in cells of hepatic origin.
authors.affiliation: Inserm U905, Université de Rouen, France. gaelle.saint-auret@cea.fr
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Saint-Auret
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Danan
authors.forename: Martine
authors.initials: M
authors.lastname: Hiron
authors.forename: Céline
authors.initials: C
authors.lastname: Blache
authors.forename: Eric
authors.initials: E
authors.lastname: Sulpice
authors.forename: Simon
authors.initials: S
authors.lastname: Tendil
authors.forename: Maryvonne
authors.initials: M
authors.lastname: Daveau
authors.forename: Xavier
authors.initials: X
authors.lastname: Gidrol
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Salier
mesh_terms: D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics* / Q000502:physiology; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000473:pathology; D016923:Cell Death / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D020869:Gene Expression Profiling; D005818:Genetic Engineering; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics* / Q000473:pathology; D008954:Models, Biological; D020411:Oligonucleotide Array Sequence Analysis; D017239:Paclitaxel / Q000494:pharmacology; D020033:Protein Isoforms / Q000235:genetics / Q000502:physiology; D019311:Staurosporine / Q000494:pharmacology; D014158:Transcription, Genetic
chemical_list: D022782:CCAAT-Enhancer-Binding Protein-beta; D020033:Protein Isoforms; D019311:Staurosporine; D017239:Paclitaxel