No abstract

In the absence of Wnt activation, cytosolic β-catenin is degraded through GSK3/CK1-mediated phosphorylation at the N terminus. Here, we show that, upon Wnt activation, the stability of nuclear β-catenin is regulated via methylation/demethylation. The protein lysine demethylases Kdm2a and Kdm2b regulate the turnover of non-phosphorylated β-catenin specifically within the nucleus via direct interaction with the fourth and fifth armadillo repeats. The lysine residues within this region are required for the methylation of non-phosphorylated β-catenin, which is demethylated by Kdm2a/b and subsequently ubiquitylated. During Xenopus embryogenesis, kdm2a/b genes are transcribed during early embryogenesis and are required for the specification of the body axis. Kdm2a/b knockdown in Xenopus embryos leads to increases in non-phosphorylated and methylated β-catenin, concurrent with the upregulation of β-catenin target genes. This mechanism is required for controlling the output of the Wnt/β-catenin signaling pathway to maintain normal cellular functions.

MicroRNAs (miRNAs, also miR) are a class of noncoding endogenous RNAs that regulate gene expression through binding to protein-coding messenger RNA (mRNA) molecules, predominantly within the 3'-untranslated region (3'-UTR). Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that regulates a battery of genes involved in regulating a variety of biological processes. There is a growing body of evidence demonstrating that miRNAs are closely associated with the STAT3 signaling pathway. In this review, we focus on interactions between miRNAs and the STAT3 signaling pathway, focusing on their reciprocal regulation and roles in cancer. For instance, several papers independently support the existence of regulatory feedback loops between miRNAs and the STAT3 pathway in different cancer contexts including IL-6-STAT3-miR-24/miR-629-HNF4α-miR-124 and IL-6R-STAT3-NF-κB-Lin-28-let-7a. Furthermore, several miRNA components are reported to be involved in STAT3-mediated tumorigenesis, for example miR-21, miR-155, and miR-181b. Through binding to STAT3-binding sites within the promoters of these oncomiRs, STAT3 activates their transcription and mediates tumorigenesis. Some miRNAs directly modulate STAT3 activity through targeting the STAT3 3'-UTR; other miRNAs target SOCS, PIAS3, and EGFR genes, which encode proteins that regulate the STAT3 signaling pathway. Given that miRNAs represent a newly discovered class of regulatory molecules, investigating their biological functions and contribution to pathologies caused by STAT3 dysregulation is essential to improve our understanding of tumorigenesis and to develop novel anticancer therapeutics. The more we can learn about miRNAs-STAT3 interactions, the better able we will be to manipulate them for developing cancer therapeutics.

Cell loss due to apoptosis induced by oxidative stress is a major hurdle for endothelial progenitor cells (EPCs)-based therapy. Sirtuin 1 (SIRT1) plays important roles in many pathophysiological processes by deacetylating various substrates, including forkhead transcription factor (FOXO). However, after deacetylation, the fate of FOXO protein remains to be explored. In the present study, we investigated whether SIRT1 exerted a protective effect on hydrogen peroxide (H(2)O(2))-induced EPCs apoptosis and, if so, what the underlying mechanism might be. EPCs were isolated and obtained from human umbilical cord blood by density gradient centrifugation and identified by morphology, tube formation ability, cell surface markers, and the ability to take up acetylated low-density lipoprotein (Dil-Ac-LDL) and bind ulex europaeus agglutinin 1 (FITC-UEA-1). Immunofluorescence showed that SIRT1 is localized in the nucleus of EPCs in the presence or absence of H(2)O(2). SIRT1 protein level in EPCs was increased by the treatment with H(2)O(2) for 24 h. Incubation of EPCs with H(2)O(2) dose dependently induced EPCs apoptosis. SIRT1 overexpression reduced the rate of EPCs apoptosis induced by H(2)O(2), whereas SIRT1 downregulation and EX527, a specific SIRT1 inhibitor, exerted the opposite effect. SIRT1 overexpression decreased the total FOXO3a protein expression, whereas SIRT1 downregulation and EX527 increased the amount of FOXO3a protein. SIRT1 reduced FOXO3a transcriptional activity according to Bim expression. Co-immunoprecipitation assay showed that SIRT1 could bind to FOXO3a, reduce its acetylation level and increase its ubiquitination level. To sum up, our work demonstrated that SIRT1 had a pivotally protective role in the regulation of EPCs apoptosis induced by H(2)O(2) and that SIRT1 protected against apoptosis by inhibiting FOXO3a via FOXO3a ubiquitination and subsequent degradation.

No abstract

Clustered regularly interspaced palindromic repeats (CRISPR) and their associated genes have been demonstrated to regulate self-genes and virulence in many pathogens. In this study, we found that inactivation of caused reduced adhesion and intracellular survival of the piscine strain GD201008-001 and significantly decreased the virulence of this strain in zebrafish and mice. Further investigation indicated that the transcriptional regulator was upregulated in the Δ mutant. As mediates the repression of hyaluronidase, a critical factor involved in opening the blood-brain barrier (BBB) in mice,-mediated repression of transcription is important for to open the BBB and thereby cause meningitis in animals. This study expands our understanding of endogenous gene regulation mediated by CRISPR-Cas systems in bacteria.

No abstract

M2 macrophages are a major component of the tumor microenvironment and are important promoters of tumor occurrence and progression. In this study, we detected large numbers of M2 macrophages in hepatocellular carcinoma tissues using immunohistochemistry and immunofluorescence. Moreover, upon oxaliplatin treatment, the M2 macrophages overexpressed interleukin-17, an important inflammatory cytokine, and thus inhibited oxaliplatin-induced apoptosis. By knocking down the interleukin-17 receptor and lysosome-associated membrane protein 2A (a key protein in chaperone-mediated autophagy) in hepatocellular carcinoma cells, we found that interleukin-17 stimulated chaperone-mediated autophagy, which further suppressed apoptosis upon oxaliplatin treatment. Chaperone-mediated autophagy induced tolerance to oxaliplatin treatment by reducing cyclin D1 expression; thus, cyclin D1 overexpression stimulated oxaliplatin-induced apoptosis. In addition, cyclin D1 expression was inhibited by interleukin-17, but increased when the interleukin-17 receptor was knocked down. Thus M2 macrophages in the hepatocellular carcinoma microenvironment generate large amounts of interleukin-17, which suppress oxaliplatin-induced tumor cell apoptosis by activating chaperone-mediated autophagy and in turn reducing cyclin D1 expression. These findings may facilitate the development of novel therapeutic strategies for chemorefractory liver cancer.