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Prohibitin1 regulates H19 and insulin‐like growth factor 2 expression in hepatocytes and liver (261.1)
Author(s) -
Ko Kwang Suk,
Yang Heping,
Li Tony,
Lee Sang Hoon,
Song Young Sun,
Lu Shelly
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.261.1
Subject(s) - gene knockdown , ctcf , microbiology and biotechnology , biology , hepatocyte , genomic imprinting , gene expression , gene , biochemistry , in vitro , dna methylation , enhancer
BACKGROUND&AIMS: Prohibitin1 (Phb1) is a ubiquitously expressed and highly conserved protein that acts as a mitochondrial chaperone and possibly as a tumor suppressor in liver. We reported liver‐specific Phb1 knockout (KO) mice develop multifocal hepatocellular carcinoma (HCC) and knockdown of Phb1 in AML12 cells (a normal hepatocyte cell line) accelerated growth. H19 and insulin‐like growth factor 2 (Igf2) are two imprinted genes often overexpressed in HCC that are induced in the Phb1 KO livers. Here we examined how Phb1 regulates their expression. METHODS : Real‐time PCR and Western blotting measured expression in Phb1 KO livers and AML12 cells treated with various siRNAs. RESULTS : H19 RNA and Igf2 mRNA and protein levels are tremendously upregulated with Phb1 deficiency in vivo (by several hundred folds) and in vitro (2‐fold after 24 hour Phb1 siRNA treatment). E2F1 and c‐Myc can activate H19 transcriptionally, but knockdown or either c‐Myc or E2F1 did not block H19 or Igf2 induction with Phb1 knockdown. Ctcf, an insulator protein that represses Igf2 expression when it is bound to the imprinting control region, is downregulated with Phb1 knockdown in AML12 cells. Double knockdown of Phb1 and Ctcf resulted in the same magnitude of H19 and Igf2 induction as single knockdown of either Phb1 or Ctcf, suggesting Phb1 may regulate the expression of H19 and Igf2 through Ctcf. Interestingly Ctcf expression is lower while H19 and IGF2 are induced in HCC samples as compared to normal liver. CONCLUSIONS : Loss of Phb1 lowers Ctcf expression, which in turn allows H19 and Igf2 gene induction to occur. Grant Funding Source : Supported by NIH R01 (R01CA172086) and NRF Korea Fund (2012R1A1A1012261)