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1.  Global analysis of DNA methylation in early-stage liver fibrosis 
Background
Liver fibrosis is caused by chemicals or viral infection. The progression of liver fibrosis results in hepatocellular carcinogenesis in later stages. Recent studies have revealed the importance of DNA hypermethylation in the progression of liver fibrosis to hepatocellular carcinoma (HCC). However, the importance of DNA methylation in the early-stage liver fibrosis remains unclear.
Methods
To address this issue, we used a pathological mouse model of early-stage liver fibrosis that was induced by treatment with carbon tetrachloride (CCl4) for 2 weeks and performed a genome-wide analysis of DNA methylation status. This global analysis of DNA methylation was performed using a combination of methyl-binding protein (MBP)-based high throughput sequencing (MBP-seq) and bioinformatic tools, IPA and Oncomine. To confirm functional aspect of MBP-seq data, we complementary used biochemical methods, such as bisulfite modification and in-vitro-methylation assays.
Results
The genome-wide analysis revealed that DNA methylation status was reduced throughout the genome because of CCl4 treatment in the early-stage liver fibrosis. Bioinformatic and biochemical analyses revealed that a gene associated with fibrosis, secreted phosphoprotein 1 (Spp1), which induces inflammation, was hypomethylated and its expression was up-regulated. These results suggest that DNA hypomethylation of the genes responsible for fibrosis may precede the onset of liver fibrosis. Moreover, Spp1 is also known to enhance tumor development. Using the web-based database, we revealed that Spp1 expression is increased in HCC.
Conclusions
Our study suggests that hypomethylation is crucial for the onset of and in the progression of liver fibrosis to HCC. The elucidation of this change in methylation status from the onset of fibrosis and subsequent progression to HCC may lead to a new clinical diagnosis.
doi:10.1186/1755-8794-5-5
PMCID: PMC3295686  PMID: 22281153
2.  The E3 Ubiquitin Ligase Activity of Trip12 Is Essential for Mouse Embryogenesis 
PLoS ONE  2011;6(10):e25871.
Protein ubiquitination is a post-translational protein modification that regulates many biological conditions [1], [2], [3], [4]. Trip12 is a HECT-type E3 ubiquitin ligase that ubiquitinates ARF and APP-BP1 [5], [6]. However, the significance of Trip12 in vivo is largely unknown. Here we show that the ubiquitin ligase activity of Trip12 is indispensable for mouse embryogenesis. A homozygous mutation in Trip12 (Trip12mt/mt) that disrupts the ubiquitin ligase activity resulted in embryonic lethality in the middle stage of development. Trip12mt/mt embryos exhibited growth arrest and increased expression of the negative cell cycle regulator p16 [7], [8], [9], [10]. In contrast, Trip12mt/mt ES cells were viable. They had decreased proliferation, but maintained both the undifferentiated state and the ability to differentiate. Trip12mt/mt ES cells had increased levels of the BAF57 protein (a component of the SWI/SNF chromatin remodeling complex) and altered gene expression patterns. These data suggest that Trip12 is involved in global gene expression and plays an important role in mouse development.
doi:10.1371/journal.pone.0025871
PMCID: PMC3196520  PMID: 22028794

Results 1-2 (2)