Characterization of a novel PXR isoform with potential dominant-negative properties.
J Hepatol
; 61(3): 609-16, 2014 Sep.
Article
em En
| MEDLINE
| ID: mdl-24798619
ABSTRACT
BACKGROUND & AIMS:
The nuclear Pregnane X Receptor (PXR, NR1I2) plays a pivotal role in xenobiotic metabolism. Here, we sought to characterize a new PXR isoform (hereafter called small PXR or sPXR) stemming from alternative transcription starting sites downstream of a CpG Island located near exon 3 of the human PXR gene.METHODS:
Quantitative RT-PCR, western blot, methylation-specific PCR, luciferase reporter assays, electro-mobility shift assays, and stable sPXR overexpression were used to examine sPXR expression and function in hepatocellular cell lines, healthy human liver (n=99), hepatocellular adenomas (HCA, n=91) and hepatocellular carcinoma samples (HCC, n=213).RESULTS:
Liver sPXR mRNA expression varied importantly among individuals and encodes a 37kDa nuclear protein consisting of the ligand-binding domain of PXR that behaves as a dominant-negative of PXR transactivation properties. In vitro methylation of the sPXR upstream promoter abolished its activity, while the demethylation agent 5-aza-2-deoxycytidine increased sPXR mRNA expression in several cell lines. Finally, we observed that sPXR mRNA expression displayed significant differences related to HCA or HCC biology.CONCLUSIONS:
This novel PXR isoform, displaying a dominant-negative activity and regulated by DNA methylation, is associated with outcomes of patients with HCC treated by resection, suggesting that it represents a key modulator of PXR.Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Receptores de Esteroides
/
Adenoma de Células Hepáticas
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Carcinoma Hepatocelular
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Fígado
/
Neoplasias Hepáticas
Limite:
Humans
Idioma:
En
Revista:
J Hepatol
Assunto da revista:
GASTROENTEROLOGIA
Ano de publicação:
2014
Tipo de documento:
Article