The hypertrehalosaemic neuropeptide conformational twins of cicadas consist of only l-amino acids: are they cis–trans isomers?

Amino Acids - It is known for almost 25 years that the corpora cardiaca (neurosecretory glands) of cicadas synthesize two isobaric peptides with hypertrehalosaemic activity denominated...     

Positive Selection and Enhancer Evolution Shaped Lifespan and Body Mass in Great Apes

Within primates, the great apes are outliers both in terms of body size and lifespan, since they include the largest and longest-lived species in the order. Yet, the molecular bases underlying such features are poorly understood. Here, we leveraged an integrated approach to investigate multiple sources of molecular variation across primates, focusing on over 10,000 genes, including approximately 1,500 previously associated with lifespan, and additional approximately 9,000 for which an association with longevity has never been suggested. We analyzed dN/dS rates, positive selection, gene expression (RNA-seq), and gene regulation (ChIP-seq). By analyzing the correlation between dN/dS, maximum lifespan, and body mass, we identified 276 genes whose rate of evolution positively correlates with maximum lifespan in primates. Further, we identified five genes, important for tumor suppression, adaptive immunity, metastasis, and inflammation, under positive selection exclusively in the great ape lineage. RNA-seq data, generated from the liver of six species representing all the primate lineages, revealed that 8% of approximately 1,500 genes previously associated with longevity are differentially expressed in apes relative to other primates. Importantly, by integrating RNA-seq with ChIP-seq for H3K27ac (which marks active enhancers), we show that the differentially expressed longevity genes are significantly more likely than expected to be located near a novel “ape-specific” enhancer. Moreover, these particular ape-specific enhancers are enriched for young transposable elements, and specifically SINE–Vntr–Alus. In summary, we demonstrate that multiple evolutionary forces have contributed to the evolution of lifespan and body size in primates.     

The binding of heparin to spike glycoprotein inhibits SARS-CoV-2 infection by three mechanisms

Heparin, a naturally occurring glycosaminoglycan, has been found to have antiviral activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative virus of COVID-19. To elucidate the mechanistic basis for the antiviral activity of heparin, we investigated the binding of heparin to the SARS-CoV-2 spike glycoprotein by means of sliding window docking, molecular dynamics simulations, and biochemical assays. Our simulations show that heparin binds at long, positively charged patches on the spike glycoprotein, thereby masking basic residues of both the receptor-binding domain (RBD) and the multifunctional S1/S2 site. Biochemical experiments corroborated the simulation results, showing that heparin inhibits the furin-mediated cleavage of spike by binding to the S1/S2 site. Our simulations showed that heparin can act on the hinge region responsible for motion of the RBD between the inactive closed and active open conformations of the spike glycoprotein. In simulations of the closed spike homotrimer, heparin binds the RBD and the N-terminal domain of two adjacent spike subunits and hinders opening. In simulations of open spike conformations, heparin induces stabilization of the hinge region and a change in RBD motion. Our results indicate that heparin can inhibit SARS-CoV-2 infection by three mechanisms: by allosterically hindering binding to the host cell receptor, by directly competing with binding to host heparan sulfate proteoglycan coreceptors, and by preventing spike cleavage by furin. Furthermore, these simulations provide insights into how host heparan sulfate proteoglycans can facilitate viral infection. Our results will aid the rational optimization of heparin derivatives for SARS-CoV-2 antiviral therapy.     

Stereotactic radiotherapy for brain oligometastases

Brain metastases, the most common metastases in adults, will develop in up to 40% of cancer patients, accounting for more than one-half of all intracranial tumors. They are most associated with breast and lung cancer, melanoma and, less frequently, colorectal and kidney carcinoma.Magnetic resonance imaging (MRI) is the gold standard for diagnosis. For the treatment plan, computed tomography (CT ) images are co-registered and fused with a gadolinium-enhanced T1-weighted MRI where tumor volume and organs at risk are contoured. Alternatively, plain and contrast-enhanced CT scans are co-registered. Single-fraction stereotactic radiotherapy (SRT ) is used to treat patients with good performance status and up to 4 lesions with a diameter of 30 mm or less that are distant from crucial brain function areas. Fractionated SRT (2–5 fractions) is used for larger lesions, in eloquent areas or in proximity to crucial or surgically inaccessible areas and to reduce treatment-related neurotoxicity. The single-fraction SRT dose, which depends on tumor diameter, impacts local control. Fractionated SRT may encompass different schedules. No randomized trial data compared the safety and efficacy of single and multiple fractions. Both single-fraction and fractionated SRT provide satisfactory local control rates, tolerance, a low risk of transient acute adverse events and of radiation necrosis the incidence of which correlated with the irradiated brain volume.     

Helix induction potential of N-terminal α-methyl, α-amino acids

Summary A series of longer analogues of the C-peptide of RNAse A has been synthesized with the aim of assessing the helix induction potential in water of α-methyl, α-amino acids at the N-terminus of the chain. The circular dichroism data indicate that one isovaline residue is effective in increasing the helix content of the 13-residue peptide by about 7%.     

Characterization of Interactions between the Mammalian Polycomb-Group Proteins Enx1/EZH2 and EED Suggests the Existence of Different Mammalian Polycomb-Group Protein Complexes

In Drosophila melanogaster, the Polycomb-group (PcG) and trithorax-group (trxG) genes have been identified as repressors and activators, respectively, of gene expression. Both groups of genes are required for the stable transmission of gene expression patterns to progeny cells throughout development. Several lines of evidence suggest a functional interaction between the PcG and trxG proteins. For example, genetic evidence indicates that the enhancer of zeste [E(z)] gene can be considered both a PcG and a trxG gene. To better understand the molecular interactions in which the E(z) protein is involved, we performed a two-hybrid screen with Enx1/EZH2, a mammalian homolog of E(z), as the target. We report the identification of the human EED protein, which interacts with Enx1/EZH2. EED is the human homolog of eed, a murine PcG gene which has extensive homology with the Drosophila PcG gene extra sex combs (esc). Enx1/EZH2 and EED coimmunoprecipitate, indicating that they also interact in vivo. However, Enx1/EZH2 and EED do not coimmunoprecipitate with other human PcG proteins, such as HPC2 and BMI1. Furthermore, unlike HPC2 and BMI1, which colocalize in nuclear domains of U-2 OS osteosarcoma cells, Enx1/EZH2 and EED do not colocalize with HPC2 or BMI1. Our findings indicate that Enx1/EZH2 and EED are members of a class of PcG proteins that is distinct from previously described human PcG proteins.In Drosophila melanogaster, the genes of the Polycomb group (PcG) and trithorax group (trxG) are part of a cellular memory system, which is responsible for the stable inheritance of gene activity. The PcG and trxG genes have been identified in Drosophila as repressors (PcG) (18, 22, 27, 28, 38) and activators (trxG) (20, 21), respectively, of homeotic gene activity. PcG and trxG genes were originally found in Drosophila, but mammalian homologs have also been identified and appear to function like their Drosophila homologs (reviewed in reference 37). It has been proposed that PcG proteins repress gene expression through the formation of multimeric protein complexes. We have recently shown that the human PcG proteins HPH1 and HPH2 coimmunoprecipitate, cofractionate, and colocalize in nuclear domains with the human PcG proteins BMI1 (2, 12, 33) and HPC2, a recently identified, novel human Polycomb protein (33, 34). Furthermore, we have found that the human RING1 protein coimmunoprecipitates and colocalizes with HPC2 and other PcG proteins, indicating that RING1 is associated with, or is part of, the mammalian PcG complex (33, 35). These results indicate that mammalian PcG proteins form a multimeric protein complex. This observation is in agreement with observations that different PcG proteins, including Pc, bind in overlapping patterns on polytene chromosomes in Drosophila salivary gland cells (4, 10, 29).Interestingly, also the trithorax gene product trx colocalizes with Drosophila PcG proteins at many sites on polytene chromosomes (6, 24). Even more strikingly, binding of the trx protein has been mapped to small DNA fragments that also contain binding sites for PcG proteins, the Polycomb response elements (5, 6). This finding is further substantiated by the observation that GAGA factor, the gene product of the trxG gene trithorax-like (Trl) (13), colocalizes with Pc protein within the close vicinity of a Polycomb response element (41). Furthermore, the PcG gene Enhancer of zeste [E(z)] contains a domain with sequence homology with the activator protein trx (17). This observation is in agreement with genetic data which indicate that E(z) can be considered both a PcG gene and a trxG gene (26). Double mutations of E(z) and trxG genes result in homeotic phenotypes which are similar to the homeotic phenotypes which are also observed in double mutants of trxG genes (26). Finally, polytene chromosome binding of the trx protein is strongly reduced in homozygous E(z) mutants (4), and vice versa, polytene chromosome binding of the E(z) protein is reduced in trx mutants (24). These data suggest functional interactions between activators (trxG proteins) and repressors (PcG proteins) that are important for their mode of action.To start to investigate these puzzling features of the E(z) gene product, we used the two-hybrid system (8, 9) in order to identify proteins that interact with a mammalian homolog of E(z), the Enx1/EZH2 protein (15, 16). Here, we report the identification of the human EED protein, which interacts with Enx1/EZH2. EED is the human homolog of eed, a murine PcG gene (7, 36) which has extensive homology with the Drosophila PcG gene extra sex combs (esc) (14, 32, 39). Whereas Enx1/EZH2 and EED coimmunoprecipitate, they neither coimmunoprecipitate nor colocalize with other human PcG proteins, such as HPC2 and BMI1. Our findings indicate that both Enx1/EZH2 and EED form a class of mammalian PcG proteins that is distinct from previously described human PcG proteins.     

Multilocus enzyme electrophoresis analysis of Trypanosoma cruzi isolates from a geographically restricted endemic area for Chagas' disease in Argentina

A set of 65 Trypanosoma cruzi stocks from dogs, opossums, insect vectors and humans was isolated in a geographically restricted endemic area for Chagas' disease in Argentina and was analysed by multilocus enzyme electrophoresis for 15 loci. The results show that at least five multilocus genotypes (clonets) circulate in the study area, one belonging to T. cruzi IIe, one to T. cruzi IId and three clonets belonging to T. cruzi I; and they confirm the presence of these lineages in the country. The three clonets attributed to T. cruzi I were identical to each other for all loci except for Sod-2, where three different patterns were identified. These patterns suggest the presence of two homozygous genotypes and one heterozygous genotype. Our results also suggest association of clonet IIe with dogs, clonet IId with humans and the three T. cruzi I clonets with Didelphis albiventris. On the other hand, there was no significant association between Triatoma infestans and any particular clonet circulating in the area. These findings are consistent with the hypothesis of natural selection, from mixed populations of T. cruzi in vectors, toward more restricted populations in mammals. The epidemiological implications of the possible selection of different clonets by different mammal hosts and the significance of two homozygous genotypes and one heterozygous genotype for the Sod-2 locus are discussed.     

Interaction between gfp-tagged Pseudomonas tolaasii P12 and Pleurotus eryngii

Pseudomonas sp., (formerly reported as strain P12) which produces brown blotch disease symptoms on Pleurotus eryngii, has been identified as P. tolaasii based on its biochemical, physiological properties and 16S rDNA sequence analysis. This pathogen is able to infect basidiocarps when surface-inoculated on mushroom casing soil. However, infected basidiocarps develop the brown blotch disease symptoms when the pathogen concentration in the fruiting body tissues is higher than 10(4) cfu/g d.w. Using gfp-tagged cells and confocal laser scanning microscopy, it was possible to show that the pathogen has the ability to tightly attach to the hyphae of Pleurotus eryngii.     

Brain Pharmacokinetics of Non‐Imidazole Biphenyl H3 Receptor Antagonists: a Liquid Chromatography/Electrospray‐Mass Spectrometry and ex vivo Binding Study in Rats

In the present article, we report on the kinetics of brain penetration in rats of the H3R antagonist 1,1′‐[1,1′‐biphenyl‐4,4′‐diylbis(methylene)]bis‐[piperidine] ( 1 ), which had shown a favorable in vitro pharmacological profile and in vivo potency in preventing scopolamine‐induced amnesia. Two different approaches were employed: high‐performance liquid chromatography/electrospray‐mass spectrometry (HPLC/ESI‐MS) and ex vivo binding against the labeled agonist [³H]‐(R)‐α‐methylhistamine ([³H]RAMHA). Starting from the structure of 1 , the rigid piperidine ring was replaced by a flexible dipropylamino group (see 2 ) or by a morpholino ring (see 3 ), endowed with lower basicity. The effect of replacement on rat plasma and brain disposition in the 24 h after administration was analyzed. High (μM ) and persistent concentrations of 1 were found in rat plasma, while plasma levels were significantly lower (range: 0–200 nM ) for the other two derivatives. This could be explained, among other factors, by the higher stability, observed for 1 , to liver metabolic cleavage. The applied chemical modulation had an important effect on in vivo brain disposition, as, despite the comparable physico‐chemical properties, 2 did not show the tendency to accumulate within the brain, as stated by its brain vs. plasma concentration ratios, if compared to 1 . These structure? property relationships should be taken into account in the pharmacokinetic optimization of new series of H3 receptor antagonists.