Increased Arf/p53 activity in stem cells,aging and cancer

Arf/p53 pathway protects the cells against DNA damage induced by acute stress. This characteristic is the responsible for its tumor suppressor activity. Moreover, it regulates the chronic type of stress associated with aging. This is the basis of its anti‐aging activity. Indeed, increased gene dosage of Arf/p53 displays elongated longevity and delayed aging. At a cellular level, it has been recently shown that increased dosage of Arf/p53 delays age‐associated stem cell exhaustion and the subsequent decline in tissue homeostasis and regeneration. However, p53 can also promote aging if constitutively activated. In this context, p53 reduces tissue regeneration, which correlates with premature exhaustion of stem cells. We discuss here the current evidence linking the Arf/p53 pathway to the processes of aging and cancer through stem cell regulation.     

Proprotein convertases blockage up-regulates specifically metallothioneins coding genes in human colon cancer stem cells

Despite continuous exertion made, colon cancer still represents a major health problem and its incidence continues being high worldwide. There is growing evidence in support of the cancer stem cells (CSCs) being central in the initiation of this cancer, and CSCs have been the focus of various studies for the identification of new ways of treatment. Lately, the proprotein convertases (PCs) were reported to regulate the maturation and expression of various molecules involved in the malignant phenotype of colon cancer cells, however, the identity of the molecules regulated by these serine proteases in CSCs is unknown. In this study, we used the general PCs inhibitor, the Decanoyl-RVKR-chloromethylketone (Decanoyl-RVKR-CMK) that inhibits all the PCs found in the secretory pathway, and analyzed its effect on CSCs using RNA-seq analysis. Remarkably, from the only 9 up-regulated genes in the human SW620-derived sphere-forming cells, we identified 7 of the 11 human metallothioneins, all of them localized on chromosome 16, and zinc related proteins as downstream effectors of the PCs. The importance of these molecules in the regulation of cell proliferation, differentiation and chemoresistance, and their reported potential tumor suppressor role and loss in colon cancer patients associated with worse prognosis, suggests that targeting PCs in the control of the malignant phenotype of CSCs is a new potential therapeutic strategy in colon cancer.     

Oxidation of 1-hydroxybenzotriazole by laccase and lignin peroxidase

A method to measure laccase and lignin peroxidase (LiP) activity at 408 nm (402–410 nm) using 1-hydroxybenzotriazole (HBT) was developed. The assay can be performed either as a kinetic measurement or as a stopped reaction using 5 mM Na-azide which improves the spectrum. Only white-rot fungal laccases and LiP were found to oxidize HBT to give shoulders or peaks at 402-410 nm. Phanerochaete and Phlebia manganese peroxidases did not give absorbance increase at 402–410 nm. © Rapid Science Ltd. 1998     

The importance of phenol oxidase activity in lignin degradation by the white-rot fungus Sporotrichum pulverulentum

The lignin degradation abilities of wildtype, a phenol oxidase-less mutant and a phenol oxidase-positive revertant of Sporotrichum pulverulentum were compared to determine if phenol oxidase activity is necessary for lignin degradation by white-rot fungi. The phenol oxidase-less mutant was unable to degrade kraft lignin or wood. The phenol oxidase-positive revertant, however, regained the ability of the wildtype to degrade kraft lignin and all of the major components of wood. It was found that kraft lignin and lignin-related phenols decreased cellulase and xylanase production by the phenol oxidase-less mutant. Addition of highly purified laccase increased the production of endo-1,4--glucanase in the phenol oxidase-less mutant in the presence of vanillic acid and kraft lignin. After addition of laccase to kraft lignin agar plates, the phenol oxidase-less mutant could degrade kraft lignin.It is proposed that phenol oxidase function in regulating the production of both lignin-and polysaccharide-degrading enzymes by oxidation of lignin and lignin-related phenols when S. pulverulentum is growing on wood.Abbreviation WT wildtype Sporotrichum pulverulentum Research supported by a grant from Stiftelsen Nils and Dorthi Troëdssons forskningsfond     

Methanol formation during lignin degradation by Phanerochaete chrysosporium

Summary Methanol formation during the degradation of synthetic lignin (DHP), spruce and birch milled wood lignin (MWL) by Phanerochaete chrysosporium Burds. was studied under different culture conditions. When 100-ml flasks with 15–20 ml volumes of culture media containing high glucose and low nitrogen concentrations were used the metabolism of methanol to formaldehyde, formic acid and CO₂ was repressed thereby facilitating methanol determination. In standing cultures with oxygen flushing the fungus converted up to 25% of the DHP-methoxyl groups to methanol and 0.5–1.5% to ¹⁴CO₂ within 22–24 h. Methanol formation from methoxyl-labelled DHP was strongly repressed by high nitrogen in the medium, by addition of glutamic acid and by culture agitation. These results indicate that methanol is formed only under ligninolytic conditions and during secondary metabolism. Methanol is most likely released both from the lignin polymer itself and from lignin degradation products. Methanol was also formed from MWL preparations with higher percentage yields produced from birch as compared to spruce MWL.Small amounts of methanol detected in cultures without lignin probably emanated from demethoxylation of veratryl alcohol synthesized de novo from glucose by the fungus during secondary metabolism. Catalase or superoxide dismutase added to the fungal culture prior to addition of lignin, did not decrease methanol formation. Horseradish peroxidase plus H₂O₂ in vitro caused 5–7% demethoxylation of O¹⁴CH₃-DHP in 22 h, while laccase gave smaller amounts of methanol (1.8%). Since addition of H₂O₂ gave similar results as peroxidase plus H₂O₂, it seems likely that the main effect of peroxidase demethoxylation emanates from the hydrogen peroxide.     

A comparison of DNA- and RNA-based clone libraries from the same marine bacterioplankton community

Clones from the same marine bacterioplankton community were sequenced, 100 clones based on DNA (16S rRNA genes) and 100 clones based on RNA (16S rRNA). This bacterioplankton community was dominated by alpha-Proteobacteria in terms of repetitive DNA clones (52%), but gamma-Proteobacteria dominated in terms of repetitive RNA clones (44%). The combined analysis led to a characterization of phylotypes otherwise uncharacterized if only the DNA or RNA libraries would have been analyzed alone. Of the DNA clones, 25.5% were found only in this library and no close relatives were detected in the RNA library. For clones from the RNA library, 21.5% of RNA clones did not indicate close relatives in the DNA library. Based on the comparisons between DNA and RNA libraries, our data indicate that the characterization of the bacterial community based on RNA has the potential to characterize distinct phylotypes from the marine environment, which remain undetected on the DNA level.     

A strategy to study <Emphasis Type="Italic">tyrosinase</Emphasis> transgenes in mouse melanocytes

Background  

A number of transgenic mice carrying different deletions in the Locus Control Region (LCR) of the mouse tyrosinase (Tyr) gene have been developed and analysed in our laboratory. We require melanocytes from these mice, to further study, at the cellular level, the effect of these deletions on the expression of the Tyr transgene, without potential interference with or from the endogenous Tyr alleles. It has been previously reported that it is possible to obtain and immortalise melanocyte cell cultures from postnatal mouse skin.     

Delta-aminolevulinic acid dehydratase (ALAD) activity in blood of Bufo arenarum (Anura)

The aim of the present investigation was to standardize a method for measuring delta-aminolevulinic acid dehydratase (ALAD) activity in circulating red blood cells of adult Bufo arenarum kept in controlled environmental conditions, and to obtain reference basal values suitable for environmental monitoring of lead exposure. The normal ALAD activity for B. arenarum was 131.86 +/- 14.47 U per liter of red blood cells (n = 38, mean +/- SEM; interval 72.98-236.33). In animals exposed to lead, ALAD activity decreased as lead dose increased.