Molecular Basis for the Anchoring of Proto-Oncoprotein Nup98 to the Cytoplasmic Face of the Nuclear Pore Complex

The cytoplasmic filament nucleoporins of the nuclear pore complex (NPC) are critically involved in nuclear export and remodeling of mRNA ribonucleoprotein particles and are associated with various human malignancies. Here, we report the crystal structure of the Nup98 C-terminal autoproteolytic domain, frequently missing from leukemogenic forms of the protein, in complex with the N-terminal domain of Nup82 and the C-terminal tail fragment of Nup159. The Nup82 β propeller serves as a noncooperative binding platform for both binding partners. Interaction of Nup98 with Nup82 occurs through a reciprocal exchange of loop structures. Strikingly, the same Nup98 groove promiscuously interacts with Nup82 and Nup96 in a mutually excusive fashion. Simultaneous disruption of both Nup82 interactions in yeast causes severe defects in mRNA export, while the severing of a single interaction is tolerated. Thus, the cytoplasmic filament network of the NPC is robust, consistent with its essential function in nucleocytoplasmic transport

Sulfur-Oxidizing Symbionts without Canonical Genes for Autotrophic CO2 Fixation

Many animals and protists depend on symbiotic sulfur-oxidizing bacteria as their main food source. These bacteria use energy from oxidizing inorganic sulfur compounds to make biomass autotrophically from CO2, serving as primary producers for their hosts. Here we describe a clade of nonautotrophic sulfur-oxidizing symbionts, “Candidatus Kentron,” associated with marine ciliates. They lack genes for known autotrophic pathways and have a carbon stable isotope fingerprint heavier than other symbionts from similar habitats. Instead, they have the potential to oxidize sulfur to fuel the uptake of organic compounds for heterotrophic growth, a metabolic mode called chemolithoheterotrophy that is not found in other symbioses. Although several symbionts have heterotrophic features to supplement primary production, in Kentron they appear to supplant it entirely.Since the discovery of symbioses between sulfur-oxidizing (thiotrophic) bacteria and invertebrates at hydrothermal vents over 40 years ago, it has been assumed that autotrophic fixation of CO2 by the symbionts drives these nutritional associations. In this study, we investigated “Candidatus Kentron,” the clade of symbionts hosted by Kentrophoros, a diverse genus of ciliates which are found in marine coastal sediments around the world. Despite being the main food source for their hosts, Kentron bacteria lack the key canonical genes for any of the known pathways for autotrophic carbon fixation and have a carbon stable isotope fingerprint that is unlike other thiotrophic symbionts from similar habitats. Our genomic and transcriptomic analyses instead found metabolic features consistent with growth on organic carbon, especially organic and amino acids, for which they have abundant uptake transporters. All known thiotrophic symbionts have converged on using reduced sulfur to gain energy lithotrophically, but they are diverse in their carbon sources. Some clades are obligate autotrophs, while many are mixotrophs that can supplement autotrophic carbon fixation with heterotrophic capabilities similar to those in Kentron. Here we show that Kentron bacteria are the only thiotrophic symbionts that appear to be entirely heterotrophic, unlike all other thiotrophic symbionts studied to date, which possess either the Calvin-Benson-Bassham or the reverse tricarboxylic acid cycle for autotrophy

Dynamic metabolic rewiring enables efficient acetyl-CoA assimilation in Paracoccus denitrificans

During growth, microorganisms have to balance metabolic flux between energy and biosynthesis. One of the key intermediates in central carbon metabolism is acetyl-CoA, which can be either oxidized in the citric acid cycle or assimilated into biomass through dedicated pathways. Two acetyl-CoA assimilation strategies have been described in bacteria so far, the ethylmalonyl-CoA pathway (EMCP) and the glyoxylate cycle (GC). Here, we show that Paracoccus denitrificans uses both strategies for acetyl-CoA assimilation during different growth stages, revealing an unexpected metabolic complexity in the organism’s central carbon metabolism. The EMCP is constitutively expressed on various substrates and leads to high biomass yields on substrates requiring acetyl-CoA assimilation, such as acetate, while the GC is specifically induced on these substrates, enabling fast growth rates. Even though each acetyl-CoA assimilation strategy alone confers a distinct growth advantage, P. denitrificans recruits both to adapt to changing environmental conditions, such as a switch from succinate to acetate. Time-resolved single-cell experiments show that during this switch, expression of the EMCP and GC is highly coordinated, indicating fine-tuned genetic programming. The dynamic metabolic rewiring of acetyl-CoA assimilation is an evolutionary innovation by P. denitrificans that allows this organism to respond in a highly flexible manner to changes in the nature and availability of the carbon source to meet the physiological needs of the cell, representing a new phenomenon in central carbon metabolism

Implementation of the β-hydroxyaspartate cycle increases growth performance of Pseudomonas putida on the PET monomer ethylene glycol

Ethylene glycol (EG) is a promising next generation feedstock for bioprocesses. It is a key component of the ubiquitous plastic polyethylene terephthalate (PET) and other polyester fibers and plastics, used in antifreeze formulations, and can also be generated by electrochemical conversion of syngas, which makes EG a key compound in a circular bioeconomy. The majority of biotechnologically relevant bacteria assimilate EG via the glycerate pathway, a wasteful metabolic route that releases CO2 and requires reducing equivalents as well as ATP. In contrast, the recently characterized β-hydroxyaspartate cycle (BHAC) provides a more efficient, carbon-conserving route for C2 assimilation. Here we aimed at overcoming the natural limitations of EG metabolism in the industrially relevant strain Pseudomonas putida KT2440 by replacing the native glycerate pathway with the BHAC. We first prototyped the core reaction sequence of the BHAC in Escherichia coli before establishing the complete four-enzyme BHAC in Pseudomonas putida. Directed evolution on EG resulted in an improved strain that exhibits 35% faster growth and 20% increased biomass yield compared to a recently reported P. putida strain that was evolved to grow on EG via the glycerate pathway. Genome sequencing and proteomics highlight plastic adaptations of the genetic and metabolic networks in response to the introduction of the BHAC into P. putida and identify key mutations for its further integration during evolution. Taken together, our study shows that the BHAC can be utilized as 'plug-and-play' module for the metabolic engineering of two important microbial platform organisms, paving the way for multiple applications for a more efficient and carbon-conserving upcycling of EG in the future.Microbial Biotechnolog

Investigation of daytime wetting: when is spinal cord imaging indicated?

Aim: To clarify indications for magnetic resonance imaging (MRI) of the spine in children with voiding dysfunction. Methods: Retrospective study of children with voiding dysfunction referred from the Guy's Hospital neurourology clinic for MRI spine between April 1998 and April 2000. Clinical notes and results of investigations, including urodynamic studies and MRI spine were reviewed. Results: There were 48 children (median age 9.1 years). Closed spina bifida was detected in five, of whom four had neuropathic vesicourethral dysfunction confirmed by urodynamic studies. Impaired bladder sensation and incomplete bladder emptying were more frequent in these children than in those with normal MRI spine. One child with spinal cord abnormality had no cutaneous, neuro-orthopaedic, or lumbosacral spine x ray abnormalities. Conclusion: Spinal cord imaging should be considered in children with daytime wetting when this is associated with impaired bladder sensation or poor bladder emptying, even in the absence of neuro-orthopaedic, cutaneous, or lumbosacral spine x ray abnormalities

Dangerously Informed: Voter Information and Pre-Electoral Violence in Africa

A considerable literature examines the effect of voter information on candidate strategies and voter-politician interactions in the developing world. The voter information literature argues that information can improve accountability because more informed voters are harder to woo with traditional campaign tools, such as ethnic appeals and vote-buying. However, this literature has largely ignored the reaction of political candidates and thus may reach conclusions that are overly optimistic regarding the impact of information on electoral accountability. We argue that voter information can increase electoral violence in developing countries where politicians face fewer institutional constraints on their campaign tactics. When violence is used as a campaign strategy, more informed electorates are more at risk because they are harder to sway through alternative campaign techniques. Using data from 35 African countries, we show that respondents receiving their news predominantly from newspapers are a good proxy for informed voters because they differ in terms of their political attitudes from respondents consuming no news or receiving it via other channels. Combining the geocoded survey data with pre-electoral violence event data, we find a robust positive association between newspaper readership and fear of and exposure to campaign violence. This finding contributes to the micro-foundations of election violence and adds a cautionary note for voter information programs