Estrogen is a growth factor that stimulates cell proliferation. The effects of estrogen are mediated through the estrogen receptors, ER␣ and ER, which function as ligand-induced transcription factors and belong to the nuclear receptor superfamily. On the other hand, TGF- acts as a cell growth inhibitor, and its signaling is transduced by Smads. Although a number of studies have been made on the cross-talk between estrogen/ER␣ and TGF-/Smad signaling, whose molecular mechanisms remain to be determined. Here, we show that ER␣ inhibits TGF- signaling by decreasing Smad protein levels. ER␣-mediated reductions in Smad levels did not require the DNA binding ability of ER␣, implying that ER␣ opposes the effects of TGF- via a novel non-genomic mechanism. Our analysis revealed that ER␣ formed a protein complex with Smad and the ubiquitin ligase Smurf, and enhanced Smad ubiquitination and subsequent degradation in an estrogen-dependent manner. Our observations provide new insight into the molecular mechanisms governing the non-genomic functions of ER␣.
Resistance rates for both clarithromycin and metronidazole appear to reflect the annual consumption of these agents. The high rate of clarithromycin resistance in Japan suggests that the effectiveness of clarithromycin-based therapies may be compromised in the near future.
In order to develop a new method for determination of the G+C content of a DNA, preparations from 26 bacterial strains and salmon sperm were digested to form 5'-deoxyribonucleotide-monophosphates (dNMP) with nuclease PI and subjected to high performance liquid chromatography (HPLC). Chromatograms indicated excellent separation of the components, and the data analysis suggested sufficient reproducibility and reasonable A/T and G/C ratios over a wide range (39 to 72mol%) of G+C values.
BackgroundLiver 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.MethodsTo 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.ResultsThe 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.ConclusionsOur 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.
Liver X receptor (LXR) activation stimulates triglyceride (TG) accumulation in the liver. Several lines of evidence indicate that estradiol-17b (E2) reduces TG levels in the liver; however, the molecular mechanism underlying the E2 effect remains unclear. Here, we show that administration of E2 attenuated sterol regulatory element-binding protein (SREBP)-1 expression and TG accumulation induced by LXR activation in mouse liver. In estrogen receptor alpha (ERa) knockout (KO) and liver-specific ERa KO mice, E2 did not affect SREBP-1 expression or TG levels. Molecular analysis revealed that ERa is recruited to the SREBP-1c promoter through direct binding to LXR and inhibits coactivator recruitment to LXR in an E2-dependent manner. Our findings demonstrate the existence of a novel liver-dependent mechanism controlling TG accumulation through the nonclassical ER/LXR pathway. To confirm that a nonclassical ER/LXR pathway regulates ERa-dependent inhibition of LXR activation, we screened ERa ligands that were able to repress LXR activation without enhancing ERa transcriptional activity, and, as a result, we identified the phytoestrogen, phloretin. In mice, phloretin showed no estrogenic activity; however, it did reduce SREBP-1 expression and TG levels in liver of mice fed a highfat diet to an extent similar to that of E2. Conclusion: We propose that ER ligands reduce TG levels in the liver by inhibiting LXR activation through a nonclassical pathway. Our results also indicate that the effects of ER on TG accumulation can be distinguished from its estrogenic effects by a specific ER ligand. (HEPATOLOGY 2014;59:1791-1802 F atty liver, caused by triglyceride (TG) accumulation in the liver, has been associated with metabolic syndrome (MetS) and is known to trigger type 2 diabetes, atherosclerosis, and other metabolic diseases.1,2 It is desirable to elucidate the mechanism of fatty liver pathogenesis. Liver X receptors (LXRs; LXRa and LXRb) are sterol sensors and bind oxysterols to regulate genes critical to cholesterol, lipid, and glucose metabolism. 3,4 In the liver, LXRs activate lipogenesis by increasing expression of sterol regulatory element-binding protein (SREBP)-1c, which controls expression of key genes
A /?-mannanase was purified from the culture filtrate of Penicillium purpurogenum No. 618 by 1st and 2nd DEAE-cellulose column chromatographies, and subsequent Ultro-gel chromatography. The final preparation thus obtained showed a single band on polyacrylamide disc-gel and SDS-polyacrylamide gel electrophoresis. The molecular weight and isoelectric point were determined to be 57,000 and pH 4.1 by SDS-polyacrylamide gel electrophoresis and isoelectric focusing, respectively. The purified mannanase contained the following amino acids: glycine>serine>glutamic acid>alanine>aspartic acid. The mannanase exhibited maximum activity at pH 5 and 70°C, and was stable in the pH range of4.5 to 8 and at temperatures up to 65°C. The enzyme activity was not affected considerably by either metal compoundsor ethylenediaminetetraacetic acid. Copra galactomannan (Gal : Man= 1 : 14) was finally hydrolyzed to galactose, mannose and /M,4-mannobiose through the sequential actions of the purified mannanase and the a-galactosidase purified from the samestrain.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.