Characterization of the transcriptional signature of C/EBPbeta isoforms (LAP/LIP) in Hep3B cells: implication of LIP in pro-survival functions.

Abstract

BACKGROUND & AIMS:

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: Gaëlle Saint-Auret, Jean-Louis Danan, Martine Hiron, Céline Blache, Eric Sulpice, Simon Tendil, Maryvonne Daveau, Xavier Gidrol, Jean-Philippe Salier
• Journal: Journal of hepatology (J Hepatol) Vol. 54 Issue 6 Pg. 1185-94 (Jun 2011) ISSN: 1600-0641 [Electronic] Netherlands
• PMID: 21145827 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2010 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Chemical References

• CCAAT-Enhancer-Binding Protein-beta
• Protein Isoforms
• Staurosporine
• Paclitaxel

Topics

• CCAAT-Enhancer-Binding Protein-beta (genetics, physiology)
• Carcinoma, Hepatocellular (genetics, pathology)
• Cell Death (drug effects, genetics, physiology)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Cell Survival (drug effects, genetics, physiology)
• Gene Expression Profiling
• Genetic Engineering
• Humans
• Liver Neoplasms (genetics, pathology)
• Models, Biological
• Oligonucleotide Array Sequence Analysis
• Paclitaxel (pharmacology)
• Protein Isoforms (genetics, physiology)
• Staurosporine (pharmacology)
• Transcription, Genetic