SummaryIn the Gram-positive bacterium, Streptomyces coelicolor A3(2), expression of the thioredoxin system is modulated by a sigma factor called s R in response to changes in the cytoplasmic thiol±disulphide status, and the activity of s R is controlled post-translationally by an anti-sigma factor, RsrA. In vitro, the antisigma factor activity of RsrA, which contains seven cysteines, correlates with its thiol±disulphide redox status. Here, we investigate the function of RsrA in vivo. A constructed rsrA null mutant had very high constitutive levels of disulphide reductase activity and s R -dependent transcription, confirming that RsrA is a negative regulator of s R and a key sensor of thiol±disulphide status. Targeted mutagenesis revealed that three of the seven cysteines in RsrA (C11, C41 and C44) were essential for anti-sigma factor activity and that a mutant RsrA protein containing only these three cysteines was active and still redox sensitive in vivo. We also show that RsrA is a metalloprotein, containing near-stoichiometric amounts of zinc. On the basis of these data, we propose that a thiol±disulphide redox switch is formed between two of C11, C41 and C44, and that all three residues play an essential role in anti-sigma factor activity in their reduced state, perhaps by acting as ligands for zinc. Unexpectedly, rsrA null mutants were blocked in sporulation, probably as a consequence of an increase in the level of free s R .

In conclusion, by combining the whole-genome DNA methylation pattern and the gene expression profile, we identified the six genes (CCDC37, CYTL1, CDO1, SLIT2, LMO3, and SERPINB5) that are regulated by DNA methylation, and we suggest their value as target molecules for further study of SCC.

Epigenetic alterations caused by viral oncoproteins are strong initiation factors for cancer development, but their mechanisms are largely unknown. To identify the epigenetic effects of viral hepatitis B virus X (HBx) that lead to hepatocellular carcinoma (HCC), we profiled the DNA methylomes of normal and HBx transgenic mouse liver. Intriguingly, severe hypomethylation of intragenic CpG islands (CGIs) was observed in HBx liver before the full development of HCC. Normally, these CGIs were highly methylated (mCGIs) by the DNMT3L complex and marked with epigenetic signatures associated with active expression, such as H3K36me3. Hypomethylation of mCGI was caused by the downregulation of Dnmt3L and Dnmt3a due to HBx bound to their promoters, along with HDAC1. These events lead to the downregulation of many developmental regulators that could facilitate tumorigenesis. Here we provide an intriguing epigenetic regulation mediated by mCGI that is required for cell differentiation and describe a previously unidentified epigenetic role for HBx in promoting HCC development.DNA methylation | methylated CpG island | viral protein H epatocellular carcinoma (HCC) is one of the most dangerous cancers that threaten many people, especially those with hepatitis B or C virus (HBV or HCV) (1-3). However, the exact mechanisms underlying HCC are not clear because there are multiple factors, including chronic inflammation (4), genetic alteration caused by viral integration into the host genome (5), and the oncogenic actions of viral proteins (6). Although many studies have previously demonstrated that these factors, alone or in combination with other factors, are able to initiate tumorigenesis (1), the oncogenic potential of viral protein in cancer development is one of the most interesting exogenic factors that facilitates tumorigenesis, in particular, through the epigenetic regulation of infected cells (7).Epigenetic alterations in cancer cells are now regarded as one of the most important factors driving cancer initiation. Abnormal DNA methylation is the most frequently found change in many cancers and is believed to control associated gene expression without altering the DNA sequence itself (8). The transcriptional silencing of tumor suppressor genes associated with the hypermethylation of promoter regions is a typical epigenetic change in many cancers (9). The DNA hypomethylation in repeat sequences and transposable elements is known to induce chromosomal instability and mutation events (10) that lead to cancer development and progression (11). In addition, various types of cancer cells exhibit abnormal expression levels of DNA methyltransferase (DNMT) families, which probably causes global changes in DNA methylation (12).In mammalian cells, large clusters of CpG dinucleotides known as CpG islands (CGIs) appear to act as a key epigenetic element regulating gene expression. Most CGIs are found at the 5′ end of transcripts and behave as functional promoters (13).Some unmethylated intragenic and intergenic CGIs contain distinct epige...

Fasting plasma glucose (FPG) has been recognized as an important indicator for the overall glycemic state preceding the onset of metabolic diseases. So far, most indentified genome-wide association loci for FPG were derived from populations with European ancestry, with a few exceptions. To extend a thorough catalog for FPG loci, we conducted meta-analyses of 13 genome-wide association studies in up to 24,740 nondiabetic subjects with East Asian ancestry. Follow-up replication analyses in up to an additional 21,345 participants identified three new FPG loci reaching genome-wide significance in or near PDK1-RAPGEF4, KANK1, and IGF1R. Our results could provide additional insight into the genetic variation implicated in fasting glucose regulation.

Autosomal dominant polycystic kidney disease (ADPKD) is a common human genetic disease characterized by the formation of multiple fluid-filled cysts in bilateral kidneys. Although mutations in polycystic kidney disease 1 (PKD1) are predominantly responsible for ADPKD, the focal and sporadic property of individual cystogenesis suggests another molecular mechanism such as epigenetic alterations. To determine the epigenomic alterations in ADPKD and their functional relevance, ADPKD and non-ADPKD individuals were analyzed by unbiased methylation profiling genome-wide and compared with their expression data. Intriguingly, PKD1 and other genes related to ion transport and cell adhesion were hypermethylated in gene-body regions, and their expressions were downregulated in ADPKD, implicating epigenetic silencing as the key mechanism underlying cystogenesis. Especially, in patients with ADPKD, PKD1 was hypermethylated in gene-body region and it was associated with recruitment of methyl-CpG-binding domain 2 proteins. Moreover, treatment with DNA methylation inhibitors retarded cyst formation of Madin-Darby Canine Kidney cells, accompanied with the upregulation of Pkd1 expression. These results are consistent with previous studies that knock-down of PKD1 was sufficient for cystogenesis. Therefore, our results reveal a critical role for hypermethylation of PKD1 and cystogenesis-related regulatory genes in cyst development, suggesting epigenetic therapy as a potential treatment for ADPKD.