No abstract

Control of cell differentiation occurs through transcriptional mechanisms and through epigenetic modification. Using a chromatin immunoprecipitation-on-chip approach, we performed a genome-wide search for target genes of peroxisome proliferator-activated receptor ␥ (PPAR␥) and its partner protein retinoid X receptor ␣ during adipogenesis. We show that these two receptors target several genes that encode histone lysine methyltransferase SET domain proteins. The histone H4 Lys 20 (H4K20) monomethyltransferase PR-Set7/Setd8 gene is upregulated by PPAR␥ during adipogenesis, and the knockdown of PR-Set7/Setd8 suppressed adipogenesis. Intriguingly, monomethylated H4K20 (H4K20me1) levels are robustly increased toward the end of differentiation. PR-Set7/Setd8 positively regulates the expression of PPAR␥ and its targets through H4K20 monomethylation. Furthermore, the activation of PPAR␥ transcriptional activity leads to the induction of H4K20me1 modification of PPAR␥ and its targets and thereby promotes adipogenesis. We also show that PPAR␥ targets PPAR␥2 and promotes its gene expression through H4K20 monomethylation. Our results connect transcriptional regulation and epigenetic chromatin modulation through H4K20 monomethylation during adipogenesis through a feedback loop.Adipocytes play a central role in energy balance, both as reservoirs of fuel and as endocrine cells, secreting factors that regulate whole-body energy metabolism. Because of the rising incidence of obesity, understanding the adipocyte is increasingly important. The process of adipocyte differentiation represents the extraordinarily coordinated regulation of multiple transcriptional systems that direct multipotent stem-cell precursors to differentiate into fully mature, functionally distinct cell types.The 3T3-L1 preadipocyte cell line has been one of the most well-characterized and widely used models for studying adipocyte differentiation (7). C/EBP␤ and C/EBP␦ are induced very early during differentiation, and these in turn activate two critical proadipogenic transcription factors, peroxisome proliferator-activated receptor ␥ (PPAR␥) and C/EBP␣. PPAR␥ and C/EBP␣ mutually stimulate each other and mediate the transition to the adipocyte phenotype (6,15,32). Recently, a number of transcription factors have been identified as regulators of adipogenesis, including GATA2 (30, 31), the Krüp-pel-like factor (KLF) family (2, 20, 24), and Nr2f2 (35).PPAR␥, a prototypical member of the nuclear receptor superfamily, is activated by natural ligands, such as arachidonic acid metabolites and fatty acid-derived components, and by the insulin-sensitizing thiazolidinedione drugs. In white and brown preadipocyte cell lines, the activation of PPAR␥ by thiazolidinediones results in robust differentiation into adipocytes. The action of PPAR␥ is mediated by two protein isoforms: the widely expressed PPAR␥1 and PPAR␥2, which is restricted to adipose tissue. The expression of each isoform is driven by a specific promoter that confers the distinct tissue-specific expression and...

For detection of hepatocellular carcinoma (HCC) in patients with liver cirrhosis, serum ␣-fetoprotein has been widely used, but its sensitivity has not been satisfactory, especially in small, well-differentiated HCC, and complementary serum marker has been clinically required. Glypican-3 (GPC3), a heparan sulfate proteoglycan anchored to the plasma membrane, is a good candidate marker of HCC because it is an oncofetal protein overexpressed in HCC at both the mRNA and protein levels. In this study, we demonstrated that its NH 2 -terminal portion [soluble GPC3 (sGPC3)] is cleaved between Arg 358 and Ser 359 of GPC3 and that sGPC3 can be specifically detected in the sera of patients with HCC. Serum levels of sGPC3 were 4.84 ؎ 8.91 ng/ml in HCC, significantly higher than the levels seen in liver cirrhosis (1.09 ؎ 0.74 ng/ml; P < 0.01) and healthy controls (0.65 ؎ 0.32 ng/ml; P < 0.001). In well-or moderately-differentiated HCC, sGPC3 was superior to ␣-fetoprotein in sensitivity, and a combination measurement of both markers improved overall sensitivity from 50% to 72%. These results indicate that sGPC3 is a novel serological marker essential for the early detection of HCC.

Genome-wide studies reveal that transcription by RNA polymerase II (Pol II) is dynamically regulated. To obtain a comprehensive view of a single transcription cycle, we switched on transcription of five long human genes (>100 kbp) with tumor necrosis factor-␣ (TNF␣) and monitored (using microarrays, RNA fluorescence in situ hybridization, and chromatin immunoprecipitation) the appearance of nascent RNA, changes in binding of Pol II and two insulators (the cohesin subunit RAD21 and the CCCTC-binding factor CTCF), and modifications of histone H3. Activation triggers a wave of transcription that sweeps along the genes at Ϸ3.1 kbp/min; splicing occurs cotranscriptionally, a major checkpoint acts several kilobases downstream of the transcription start site to regulate polymerase transit, and Pol II tends to stall at cohesin/CTCF binding sites.endothelial cell ͉ polymerase II ͉ RNA ͉ tumor necrosis factor alpha

Inflammatory bowel disease (IBD) is defined as chronic intestinal inflammation, and includes ulcerative colitis and Crohn's disease. Multiple factors are involved in the pathogenesis of IBD, and the condition is characterized by aberrant mucosal immune reactions to intestinal microbes in genetically susceptible hosts. Transforming growth factor-b (TGF-b) is an immune-suppressive cytokine produced by many cell types and activated by integrins. Active TGF-b binds to its receptor and regulates mucosal immune reactions through the TGF-b signaling pathway. Dysregulated TGF-b signaling is observed in the intestines of IBD patients. TGF-b signal impairment in specific cell types, such as T-cells and dendritic cells, results in spontaneous colitis in mouse models. In addition, specific intestinal microbes contribute to immune homeostasis by modulating TGF-b production. In this review, we describe the role of TGF-b in intestinal immunity, focusing on immune cells, epithelium, and intestinal microbes. In addition, we present potential therapeutic strategies for IBD that target TGF-b.