Search

In prokaryotes, two-component signal transduction systems, consisting of a histidine kinase and a response regulator, play a critical role in regulating a range of cellular functions. A recent study suggests that XCC3315, a response regulator with a CheY-like receiver domain attached to an uncharacterized HD-related output domain (HDOD domain), plays a role in the general stress response of the Gram-negative bacterium Xanthomonas campestris pv. campestris (Xcc), the causal agent of black rot in cruciferous plants. Here, we demonstrated genetically that XCC3315, designated as gsmR (general stress and motility regulator), is involved in the expression of genes responsible for flagellum synthesis, including rpoN2, flhF, flhB, and fliC. Site-directed mutagenesis revealed that Glu9 and Arg100 in the receiver domain and Gly205, Asp263, His287, Trp298 and His311 in the HDOD are critical amino acids for GsmR function in cell motility regulation. The gsmR transcription initiation site was mapped. Promoter analysis and gel retardation assay revealed that the expression of gsmR is positively controlled by the global transcriptional regulator Clp in a direct manner, and is subject to catabolite repression. Our findings not only extend the previous work on Clp regulation to show that it influences the expression of gsmR in Xcc, but are also the first to characterize the expression of this response regulator gene in this phytopathogen. Furthermore, GsmR is the first HDOD-containing protein of bacteria in which key amino acids have been experimentally identified and characterized.

BACKGROUND: Glutathione S-transferases M2 (GST-M2) is a detoxifying enzyme. Low expression levels of GST-M2 have been detected in lung cancer cells. However, little is known about the regulation of GST-M2 in lung cancer cells. In this study, the authors investigated the epigenetic regulatory mechanisms of GST-M2 in lung cancer cells. METHODS: The authors evaluated the promoter methylation of GST-M2 in lung cancer cells after treatment with the DNA methyltransferase (DNMT) inhibitor 5′-aza-2′-deoxycytidine (5′-aza-dC). Reporter activity assays, chromatin immunoprecipitation (ChIP), electrophoretic mobility-shift assays, and small interfering RNA (siRNA) assays were used to determine whether the methylation of specificity protein 1 (Sp1) affected binding to the GST-M2 promoter or regulated GST-M2 transcription. Real-time polymerase chain reaction was used to determine GST-M2 and DNMT-3b messenger RNA levels in 73 nonsmall cell lung cancer (NSCLC) tissues. RESULTS: GST-M2 expression was restored after treatment with 5′-aza-dC in lung cancer cells. GST-M2 exhibited high frequency of promoter hypermethylation in lung cancer cells and NSCLC tumor tissues. CpG hypermethylation abated Sp1 binding to the GST-M2 promoter in lung cancer. Knockdown of Sp1 in normal lung cells reduced GST-M2 expression, and silencing of DNMT-3b increased GST-M2 expression in lung cancer cells. In addition, DNMT-3b expression was significantly higher in lung tumors with low levels of GST-M2 expression than in lung tumors with high levels of GST-M2 expression, especially among women and among patients who had stage I disease. CONCLUSIONS: Epigenetic silencing of GST-M2 was distinguished from Sp1-mediated GST-M2 transcriptional expression. The authors concluded that this represents a mechanism that leads to decreased expression of GST-M2 in lung cancer cells. Cancer 2011. © 2011 American Cancer Society.

Background and Objectives The aim of this study was to examine the potential associations of two hypoxia inducible factor-1α (HIF-1α) gene polymorphisms, C1772T and G1790A, with the susceptibility and clinicopathological status of hepatocellular carcinoma. Methods A total of 449 subjects, including 347 healthy controls and 102 patients with hepatocellular carcinoma, were recruited in this study and subjected to polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) analyses to estimate the impact of these two polymorphic variants on hepatocellular carcinoma. Results G1790A heterozygotes showed a higher risk for hepatocellular carcinoma, compared with GG genotypes after adjusting for other confounders (AOR = 3.97; 95%CI = 1.70–9.22), indicating a significant association between hepatocellular carcinoma susceptibility and G1790A polymorphism. Moreover, results also revealed the presence of synergistic effect between gene polymorphism of HIF-1α G1790A and environmental risk factors, such as tobacco and alcohol consumptions while there was no significant association between HIF-1α gene polymorphism and clinicopathological parameters of hepatocellular carcinoma. Conclusions Genetic polymorphism at G1790A of HIF-1α is an important factor for determining the susceptibility to hepatocellular carcinoma. The interaction effects of G1790A heterozygotes to tobacco and to alcohol consumption significantly increase the risk to develop hepatocellular carcinoma. J. Surg. Oncol. 2010;102:163–169. © 2010 Wiley-Liss, Inc.

Chronic exercise has been reported to improve cognitive function. However, whether and how different types of exercise affect various learning and memory tasks remain uncertain. To address this issue, male BALB/c mice were trained for 4 weeks under two different exercise protocols: moderate treadmill running or voluntary wheel running. After exercise training, their spatial memory and aversive memory were evaluated by a Morris water maze and by one-trial passive avoidance (PA), respectively. Levels of neural plasticity-related proteins, i.e. brain-derived neurotrophic factor (BDNF), tropomyosin-related kinase B (TrkB) and synaptotagmin I (Syt I), in hippocampus and amygdala were determined by ELISA or immunoblotting. Finally, the functional roles of these proteins in the basolateral amygdala were verified by locally blocking them with K252a (a TrkB kinase inhibitor), or lentivirus expressing Syt I shRNA. We found that (1) although both moderate treadmill running and wheel running improved the Morris water maze performance, only the former improved PA performance; (2) likewise, both exercise protocols upregulated the BDNF-TrkB pathway and Syt I in the hippocampus, whereas only treadmill exercise upregulated their expression levels in the amygdala; (3) local injection of K252a abolished the treadmill exercise-facilitated PA performance and upregulation of amygdalar TrkB and Syt I; and (4) local administration of Syt I shRNA abolished the treadmill exercise-facilitated PA performance and upregulation of amygdalar Syt I. Therefore, our results support the notion that different forms of exercise induce neuroplasticity changes in different brain regions, and thus exert diverse effects on various forms of learning and memory.