Bacterial remodelling of the host epigenome: functional role and evolution of effectors methylating host histones

The modulation of the chromatin organization of eukaryotic cells plays an important role in regulating key cellular processes including host defence mechanisms against pathogens. Thus, to successfully survive in a host cell, a sophisticated bacterial strategy is the subversion of nuclear processes of the eukaryotic cell. Indeed, the number of bacterial proteins that target host chromatin to remodel the host epigenetic machinery is expanding. Some of the identified bacterial effectors that target the chromatin machinery are ‘eukaryotic‐like’ proteins as they mimic eukaryotic histone writers in carrying the same enzymatic activities. The best‐studied examples are the SET domain proteins that methylate histones to change the chromatin landscape. In this review, we will discuss SET domain proteins identified in the Legionella, Chlamydia and Bacillus genomes that encode enzymatic activities targeting host histones. Moreover, we discuss their possible origin as having evolved from prokaryotic ancestors or having been acquired from their eukaryotic hosts during their co‐evolution. The characterization of such bacterial effectors as modifiers of the host chromatin landscape is an exciting field of research as it elucidates new bacterial strategies to not only manipulate host functions through histone modifications but it may also identify new modifications of the mammalian host cells not known before.     

Fluorescence decrease of conjugated polymers by the catalytic activity of horseradish peroxidase and its application in phenolic compounds detection

We report the fluorescence decrease of the water-soluble π-π-conjugated polymer poly(2-methoxy-5-propyloxy sulfonate phenylene vinylene, MPS-PPV) by the catalytic activity of horseradish peroxidase in the presence of H(2)O(2). MPS-PPV acts as a donor substrate in the catalytic cycle of horseradish peroxidase where the electron-deficient enzymatic intermediates compounds I and II can subtract electrons from the polymer leading to its fluorescence decrease. The addition of phenolic drug acetaminophen to the former solution favors the decrease of the polymer fluorescence, which indicates the peroxidase-catalyzed co-oxidation of MPS-PPV and acetaminophen. The encapsulation of horseradish peroxidase within polyacrylamide microgels allows the isolation of intermediates compound I and compound II from the polymer, leading to a fluorescence decrease that is only due to the product of biocatalytic acetaminophen oxidation. This system could be used to develop a new device for phenolic compounds detection.     

Comparative proteomic analysis of Fasciola hepatica juveniles and Schistosoma bovis schistosomula

Protein interactions between host and parasites can influence the infection success and severity. The aim of this investigation was to identify the proteins from two trematodes potentially localized at the host-parasite interface. We performed the proteomic profiles from in vivo obtained immature lung stage Schistosoma bovis schistosomula and in vitro excysted juveniles from Fasciola hepatica, parasites of ruminants and man usually giving rise to chronic infections. Proteomes from those parasites were obtained after digestion with trypsin and the peptides generated were identified by mass spectrometry, both before and after parasites' treatment with 70% methanol. The comparison of the two proteome sets from each parasite and between them, the analysis of their relative abundance and of their potential exposure to the host from living parasites, together with the specific immunolocalization of two of the identified molecules, show that this approach could assist in the identification of parasite exposed proteins and in the definition of molecules common for the two parasites with potential interaction with the host. Further characterization of these molecules could guide to define new common anti-parasitic targets and potential vaccine candidates.     

Balance between MKK6 and MKK3 mediates p38 MAPK associated resistance to cisplatin in NSCLC

The p38 MAPK signaling pathway has been proposed as a critical mediator of the therapeutic effect of several antitumor agents, including cisplatin. Here, we found that sensitivity to cisplatin, in a system of 7 non-small cell lung carcinoma derived cell lines, correlated with high levels of MKK6 and marked activation of p38 MAPK. However, knockdown of MKK6 modified neither the response to cisplatin nor the activation of p38 MAPK. Deeper studies showed that resistant cell lines also displayed higher basal levels of MKK3. Interestingly, MKK3 knockdown significantly decreased p38 phosphorylation upon cisplatin exposure and consequently reduced the response to the drug. Indeed, cisplatin poorly activated MKK3 in resistant cells, while in sensitive cell lines MKK3 showed the opposite pattern in response to the drug. Our data also demonstrate that the low levels of MKK6 expressed in resistant cell lines are the consequence of high basal activity of p38 MAPK mediated by the elevated levels of MKK3. This finding supports the existence of a regulatory mechanism between both MAPK kinases through their MAPK. Furthermore, our results were also mirrored in head and neck carcinoma derived cell lines, suggesting our observations boast a potential universal characteristic in cancer resistance of cisplatin. Altogether, our work provides evidence that MKK3 is the major determinant of p38 MAPK activation in response to cisplatin and, hence, the resistance associated with this MAPK. Therefore, these data suggest that the balance between both MKK3 and MKK6 could be a novel mechanism which explains the cellular response to cisplatin.     

Rational strategy for the production of new crude lipases from <Emphasis Type="BoldItalic">Candida rugosa</Emphasis>

Candida rugosa was cultured using different inducers (oleic acid, olive oil, sunflower oil, n-dodecanol and glycerol) as the only carbon source in batch conditions, as well as in several fed-batch fermentations (oleic acid as inducer) at variable feed rate conditions. The N-terminal analysis of each crude lipase revealed that, while the isoenzymes Lip2 and Lip3 are always secreted (at different proportions depending on the inducer), Lip1 was produced only using n-dodecanol (batch conditions) or oleic acid (fed-batch at high feed rate). The nature of the inducer controls the isoenzyme percentage; when this is fixed, as well as the feed rate in fed-batch fermentation, the isoenzymatic profile remained unaltered and the samples differed only in the activity of the lipases, as determined by heptyl oleate synthesis.     

Thermal death kinetics of red flour beetle (Coleoptera: Tenebrionidae)

While developing radio frequency heat treatments for dried fruits and nuts, we used a heating block system developed by Washington State University to identify the most heat-tolerant life stage of red flour beetle, Tribolium castaneum (Herbst), and to determine its thermal death kinetics. Using a heating rate of 15 degrees C/min to approximate the rapid heating of radio frequency treatments, the relative heat tolerance of red flour beetle stages was found to be older larvae > pupae and adults > eggs and younger larvae. Lethal exposure times for temperatures of 48, 50, and 52 degrees C for the most heat-tolerant larval stage were estimated using a 0.5th order kinetic model. Exposures needed for 95% mortality at 48 degrees C were too long to be practical (67 min), but increasing treatment temperatures to 50 and 52 degrees C resulted in more useful exposure times of 8 and 1.3 min, respectively. Red flour beetle was more sensitive to changes in treatment temperature than previously studied moth species, resulting in red flour beetle being the most heat-tolerant species at 48 degrees C, but navel orangeworm, Amyelois transitella (Walker), being most heat tolerant at 50 and 52 degrees C. Consequently, efficacious treatments for navel orangeworm at 50-52 degrees C also would control red flour beetle.     

抗肿瘤药阿霉素诱导Wnt通路抑制因子的表达

研究抗肿瘤药阿霉素对Wnt通路抑制因子FrpHE(frizzled-related protein)和DKK-1(Dickkopf-1)表达的作用.将抗肿瘤药阿霉素加入到人肝癌HepG2(HepG2,含野生型p53;Hep3B,p53缺失)、人大肠癌(Lovo,含野生型p53)和人神经胶质瘤细胞(U251,p53突变)细胞株中.以RT-PCR技术检测阿霉素对Wnt通路抑制因子FrpHE和DKK-1的表达调节作用,以流式细胞术检测在肿瘤细胞中Wnt通路的关键调节因子β-catenin的表达.在加入阿霉素24h后FrpHEmRNA表达水平在人肝癌细胞(HepG2,含野生型p53;Hep3B,p53缺失)中与对照组相比表达水平显著增加.在人大肠癌细胞(Lovo,含野生型p53)和人神经胶质瘤细胞(U251,p53突变型)细胞中,未见FrpHE mRNA表达.DKK-1mRNA表达水平在人肝癌细胞(HepG2,含野生型p53;Hep3B,p53缺失)、人大肠癌细胞(Lovo,含野生型p53)和人神经胶质瘤细胞(U251,p53突变型)中与对照组相比表达水平显著增加.β-catenin的阳性细胞百分比强度和平均荧光量强度与对照组相比,表达水平降低.提示化疗药阿霉素能明显诱导抑制剂FrpHEmRNA和DKK-1mRNA的表达.