A cell‐based model system links chromothripsis with hyperploidy

A remarkable observation emerging from recent cancer genome analyses is the identification of chromothripsis as a one‐off genomic catastrophe, resulting in massive somatic DNA structural rearrangements (SRs). Largely due to lack of suitable model systems, the mechanistic basis of chromothripsis has remained elusive. We developed an integrative method termed “complex alterations after selection and transformation (CAST),” enabling efficient in vitro generation of complex DNA rearrangements including chromothripsis, using cell perturbations coupled with a strong selection barrier followed by massively parallel sequencing. We employed this methodology to characterize catastrophic SR formation processes, their temporal sequence, and their impact on gene expression and cell division. Our in vitro system uncovered a propensity of chromothripsis to occur in cells with damaged telomeres, and in particular in hyperploid cells. Analysis of primary medulloblastoma cancer genomes verified the link between hyperploidy and chromothripsis in vivo. CAST provides the foundation for mechanistic dissection of complex DNA rearrangement processes.     

Further in vitro exploration fails to support the allosteric three-site model

Ongoing debate in the ribosome field has focused on the role of bound E-site tRNA and the Shine-Dalgarno-anti-Shine-Dalgarno (SD-aSD) interaction on A-site tRNA interactions and the fidelity of tRNA selection. Here we use an in vitro reconstituted Escherichia coli translation system to explore the reported effects of E-site-bound tRNA and SD-aSD interactions on tRNA selection events and find no evidence for allosteric coupling. A large set of experiments exploring the role of the E-site tRNA in miscoding failed to recapitulate the observations of earlier studies (Di Giacco, V., Márquez, V., Qin, Y., Pech, M., Triana-Alonso, F. J., Wilson, D. N., and Nierhaus, K. H. (2008) Proc. Natl. Acad. Sci. U.S.A. 105, 10715-10720 and Geigenmüller, U., and Nierhaus, K. H. (1990) EMBO J. 9, 4527-4533); the frequency of miscoding was unaffected by the presence of E-site-bound cognate tRNA. Moreover, our data provide clear evidence that the reported effects of the SD-aSD interaction on fidelity can be attributed to the binding of ribosomes to an unanticipated site on the mRNA (in the absence of the SD sequence) that provides a cognate pairing codon leading naturally to incorporation of the purported "noncognate" amino acid.     

Cyclin D1 determines mitochondrial function in vivo

The cyclin D1 gene encodes a regulatory subunit of the holoenzyme that phosphorylates and inactivates the pRb tumor suppressor to promote nuclear DNA synthesis. cyclin D1 is overexpressed in human breast cancers and is sufficient for the development of murine mammary tumors. Herein, cyclin D1 is shown to perform a novel function, inhibiting mitochondrial function and size. Mitochondrial activity was enhanced by genetic deletion or antisense or small interfering RNA to cyclin D1. Global gene expression profiling and functional analysis of mammary epithelial cell-targeted cyclin D1 antisense transgenics demonstrated that cyclin D1 inhibits mitochondrial activity and aerobic glycolysis in vivo. Reciprocal regulation of these genes was observed in cyclin D1-induced mammary tumors. Cyclin D1 thus integrates nuclear DNA synthesis and mitochondrial function.     

Influence of sampling time and sap extraction methodology on xylem pH values in two grapevine varieties grown under drought conditions

The effect of differences in applied pressure and time of sampling on pH values of xylem sap collected using the leaf pressurization technique was examined in two grapevine varieties originating from contrasting habitats (Vitis vinifera L., cvs. Sabatiano and Mavrodafni) after subjecting them to drought. Three fractions of xylem sap exudates were collected from each leaf according to differences in applied pressure; fractions (I), (II) and (III) corresponding to 1 MPa, 2 MPa and 2.5 MPa pressure, respectively. The pH values in fraction (I) were significantly lower than those in fractions (II) and (III). The sap pH values in fraction (III) seemed to better correspond to changes in leaf apoplastic pH. The time of sampling was found to strongly influence xylem pH values. In particular, a positive relationship between predawn xylem pH values and soil drying was observed. Conversely, xylem pH values measured later during the day (i.e. at 8:00, 9:00 and 10:00 am) were not significantly affected by the reduction in soil water availability in both varieties. It is suggested that the most suitable period for sap sampling in order to better discriminate drought effects on xylem sap pH is at predawn. Furthermore, there were significant differences in pH values as well as in the sensitivity of stomatal conductance to pH between the two varieties. These differences might be related to strategy differences between grapevine varieties for adaptation to drought.     

Synthesis and biological evaluation of benzopyran analogues bearing class III antiarrhythmic pharmacophores

We have synthesized a series of compounds combining the hydroxy-benzopyran ring of vitamin E with the methylsulfonylaminophenyl group of class III antiarrhythmic drugs, connected through tertiary amine moieties. Evaluation of the antiarrhythmic and antioxidant activity of the new compounds was carried out on isolated rat heart preparations using the non-recirculating Langendorff mode. The new analogues were present, at 10 microM concentration, during ischemia and reperfusion. Selected compounds were further studied by a conventional microelectrode method in order to get insight into their cellular mode of action. The most active compound, N-[4-[2-[[2-(3,4-dihydro-6-hydroxy-2,2,7,8-tetramethyl-2H-1-benzopyran-5-yl)ethyl] methylamine]ethyl]phenyl]methanesulfonamide (19a), reduces premature beats, prolongs QT and QRS intervals during ischemia and reperfusion, and reduces MDA content, leading to a fast recovery of the heart. In addition, it exhibits moderate class III antiarrhythmic action.     

Atherogenic lipid profile is a feature characteristic of patients with early rheumatoid arthritis: effect of early treatment – a prospective, controlled study

The efficiency of activating latent transforming growth factor (TGF)-β₁ in systemic lupus erythematosus (SLE) may control the balance between inflammation and fibrosis, modulating the disease phenotype. To test this hypothesis we studied the ability to activate TGF-β₁ in SLE patients and control individuals within the context of inflammatory disease activity, cumulative organ damage and early atherosclerosis. An Activation Index (AI) for TGF-β₁ was determined for 32 patients with SLE and 33 age-matched and sex-matched control individuals by quantifying the increase in active TGF-β₁ under controlled standard conditions. Apoptosis in peripheral blood mononuclear cells was determined by fluorescence-activated cell sorting. Carotid artery intima-media thickness was measured using standard Doppler ultrasound. These measures were compared between patients and control individuals. In an analysis conducted in patients, we assessed the associations of these measures with SLE phenotype, including early atherosclerosis. Both intima-media thickness and TGF-β₁ AI for SLE patients were within the normal range. There was a significant inverse association between TGF-β₁ AI and levels of apoptosis in peripheral blood mononuclear cells after 24 hours in culture for both SLE patients and control individuals. Only in SLE patients was there a significant negative correlation between TGF-β₁ AI and low-density lipoprotein cholesterol (r = -0.404; P = 0.022) and between TGF-β₁ AI and carotid artery intima-media thickness (r = -0.587; P = 0.0004). A low AI was associated with irreversible damage (SLICC [Systemic Lupus International Collaborating Clinics] Damage Index ≥1) and was inversely correlated with disease duration. Intima-media thickness was significantly linked to total cholesterol (r = 0.371; P = 0.037). To conclude, in SLE low normal TGF-β₁ activation was linked with increased lymphocyte apoptosis, irreversible organ damage, disease duration, calculated low-density lipoprotein levels and increased carotid IMT, and may contribute to the development of early atherosclerosis.     

DIVING DEVELOPMENT AND BEHAVIOR OF A REHABILITATED MEDITERRANEAN MONK SEAL (MONACHUS MONACHUS)

Among the priority actions identified for saving the critically endangered Mediterranean monk seal are gaining basic biological information on movements and behavior, and rescuing and rehabilitating wounded, stranded, and orphaned pups. On 22 May 2004 a rehabilitated monk seal juvenile was fitted with a satellite tag, released in the National Marine Park of Alonnisos, Northern Sporades, Greece, and monitored for 167 d. Postrelease, the seal remained close to the islands of the park and within the 200-m isobath. Throughout the monitoring period, the seal reduced time hauled out, while 95-percentile dive duration and depth gradually increased. The overall maximum depth of 123 m recorded in this study is the greatest depth ever recorded for the species. These results confirm the effectiveness of the rehabilitation program carried out on the particular animal and provide additional support for the continuation of the rehabilitation program as a conservation measure for the species. We demonstrate that satellite tracking of rehabilitated seals is a valuable research and conservation tool, even for a species that commonly uses shoreline caves for resting, molting, and parturition.     

Novel conformationally restricted tetracyclic analogs of delta8-tetrahydrocannabinol.

Novel analogs of (-)-delta8-tetrahydrocannabinol (delta8-THC) in which the conformation of the side chain was restricted by incorporating the first one or two carbons into a six membered ring fused with the aromatic phenolic A ring were synthesized. The affinities of the novel ligands for CB1 and CB2 indicated that the "southbound" chain conformer retained the highest affinity for both receptors.     

Polyamines affect diversely the antibiotic potency: insight gained from kinetic studies of the blasticidin S AND spiramycin interactions with functional ribosomes

The effects of spermine on peptidyltransferase inhibition by an aminohexosylcytosine nucleoside, blasticidin S, and by a macrolide, spiramycin, were investigated in a model system derived from Escherichia coli, in which a peptide bond is formed between puromycin and AcPhe-tRNA bound at the P-site of poly(U)-programmed ribosomes. Kinetics revealed that blasticidin S, after a transient phase of interference with the A-site, is slowly accommodated near to the P-site so that peptide bond is still formed but with a lower catalytic rate constant. At high concentrations of blasticidin S (>10 x K(i)), a second drug molecule binds to a weaker binding site on ribosomes, and this may account for the onset of a subsequent mixed-noncompetitive inhibition phase. Spermine enhances the blasticidin S inhibitory effect by facilitating the drug accommodation to both sites. On the other hand, spiramycin (A) was found competing with puromycin for the A-site of AcPhe-tRNA.poly(U).70 S ribosomal complex (C) via a two-step mechanism, according to which the fast formation of the encounter complex CA is followed by a slow isomerization to a tighter complex, termed C(*)A. In contrast to that observed with blasticidin S, spermine reduced spiramycin potency by decreasing the formation and stability of complex C(*)A. Polyamine effects on drug binding were more pronounced when a mixture of spermine and spermidine was used, instead of spermine alone. Our kinetic results correlate well with cross-linking and crystallographic data and suggest that polyamines bound at the vicinity of the antibiotic binding pockets modulate diversely the interaction of these drugs with ribosomes.