Global DNA hypomethylation is a hallmark of cancer cells, but its molecular mechanisms have not been elucidated. Here, we show that the disruption of Dnmt1/PCNA/UHRF1 interactions promotes a global DNA hypomethylation in human gliomas. We then demonstrate that the Dnmt1 phosphorylations by Akt and/or PKC abrogate the interactions of Dnmt1 with PCNA and UHRF1 in cellular and acelluar studies including mass spectrometric analyses and the use of primary cultured patient-derived glioma. By using methylated DNA immunoprecipitation, methylation and CGH arrays, we show that global DNA hypomethylation is associated with genes hypomethylation, hypomethylation of DNA repeat element and chromosomal instability. Our results reveal that the disruption of Dnmt1/PCNA/UHRF1 interactions acts as an oncogenic event and that one of its signatures (i.e. the low level of mMTase activity) is a molecular biomarker associated with a poor prognosis in GBM patients. We identify the genetic and epigenetic alterations which collectively promote the acquisition of tumor/glioma traits by human astrocytes and glial progenitor cells as that promoting high proliferation and apoptosis evasion.

Extreme ultraviolet photon activation tandem mass spectrometry (MS) at 69 nm (18 eV) was used to characterize mixtures of oligo-porphyrans, a class of highly sulfated oligosaccharides. Porphyrans, hybrid polymers whose structures are far from known, continue to provide a challenge for analytical method development. Activation by 18 eV photons led to a rich fragmentation of the oligo-porphyrans, with many cross-ring and glycosidic cleavages. In contrast to multistage MSn strategies such as activated electron photodetachment dissociation, a single step of irradiation by energetic UV of multiply charged anions led to a complete fragmentation of the oligo-porphyrans. In both ionization modes, the sulfate groups were retained on the backbone, which allowed the pattern of these modifications along the porphyran backbone to be described in unprecedented detail. Many structures released by the enzymatic degradation of the porphyran were completely resolved, including isomers. This work extends the existing knowledge of the structure of porphyrans. In addition, it provides a new demonstration of the potential of activation by high-energy photons for the structural analysis of oligosaccharides, even in unseparated mixtures, with a particular focus on sulfated compounds.

Imaging mass spectrometry techniques have become a powerful strategy to assess the spatial distribution of metabolites in biological systems. Based on auto-ionisability of lichen metabolites using LDI-MS, we herein image the distribution of major secondary metabolites (specialized metabolites) from the lichen Ophioparma ventosa by LDI-MSI (Mass Spectrometry Imaging). Such technologies offer tremendous opportunities to discuss the role of natural products through spatial mapping, their distribution patterns being consistent with previous chemical ecology reports. A special attention was dedicated to miriquidic acid, an unexpected molecule we first reported in Ophioparma ventosa. The analytical strategy presented herein offers new perspectives to access the sharp distribution of lichen metabolites from regular razor blade-sectioned slices.

The 7S-globulin fraction is a minor component of the amaranth storage proteins. The present work provides new information about this protein. The amaranth 7S-globulin or vicilin presented a sedimentation coefficient of 8.6 ± 0.6 S and was composed of main subunits of 66, 52, 38, and 16 kDa. On the basis of mass spectrometry (MS) analysis of tryptic fragments, the 52, 38, and 16 kDa subunits presented sequence homology with sesame vicilin, whereas the 66 kDa subunit showed sequence similarity with a putative vicilin. Several characteristics of the 66 kDa subunit were similar to members of the convicilin family. Results support the hypothesis that the 7S-globulin molecules are composed of subunits coming from at least two gene families with primary products of 66 and 52 kDa, respectively. According to the present information, amaranth vicilin may be classified into the vicilin group that includes pea, broad bean, and sesame vicilins, among others.

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