COMMD1-mediated ubiquitination regulates CFTR trafficking

The CFTR (cystic fibrosis transmembrane conductance regulator) protein is a large polytopic protein whose biogenesis is inefficient. To better understand the regulation of CFTR processing and trafficking, we conducted a genetic screen that identified COMMD1 as a new CFTR partner. COMMD1 is a protein associated with multiple cellular pathways, including the regulation of hepatic copper excretion, sodium uptake through interaction with ENaC (epithelial sodium channel) and NF-kappaB signaling. In this study, we show that COMMD1 interacts with CFTR in cells expressing both proteins endogenously. This interaction promotes CFTR cell surface expression as assessed by biotinylation experiments in heterologously expressing cells through regulation of CFTR ubiquitination. In summary, our data demonstrate that CFTR is protected from ubiquitination by COMMD1, which sustains CFTR expression at the plasma membrane. Thus, increasing COMMD1 expression may provide an approach to simultaneously inhibit ENaC absorption and enhance CFTR trafficking, two major issues in cystic fibrosis.     

Genome-wide acceleration of protein evolution in flies (Diptera)

Background

The rate of molecular evolution varies widely between proteins, both within and among lineages. To what extent is this variation influenced by genome-wide, lineage-specific effects? To answer this question, we assess the rate variation between insect lineages for a large number of orthologous genes.

Results

When compared to the beetle Tribolium castaneum, we find that the stem lineage of flies and mosquitoes (Diptera) has experienced on average a 3-fold increase in the rate of evolution. Pairwise gene comparisons between Drosophila and Tribolium show a high correlation between evolutionary rates of orthologous proteins.

Conclusion

Gene specific divergence rates remain roughly constant over long evolutionary times, modulated by genome-wide, lineage-specific effects. Among the insects analysed so far, it appears that the Tribolium genes show the lowest rates of divergence. This has the practical consequence that homology searches for human genes yield significantly better matches in Tribolium than in Drosophila. We therefore suggest that Tribolium is better suited for comparisons between phyla than the widely employed dipterans.     

Breeding mute swan habitat selection when accounting for detectability: a plastic behaviour consistent with rapidly expanding populations

A number of native and exotic animal species show dramatic population increases in terms of both numbers and geographic range. Understanding the habitat selection processes behind such increases is crucial to implement adequate management measures. Mute swan (Cygnus olor) populations have experienced a tremendous demographic and geographic expansion in Western Europe during the twentieth century, colonizing a wide variety of aquatic habitats. We aimed at assessing how swans select nesting sites during the pre-laying and laying periods on medium to large fishponds (from 10 to 50 ha) in Eastern France, while accounting for detectability biases and testing for the effects of fishpond spatial configuration, vegetation resources, human disturbance and habitat management. Our results demonstrate that the mute swan is a non-selective species regarding its nesting habitat among such fishponds, using these independently from the parameters considered although fishpond characteristics varied. Although mute swan is one of the least cryptic Anatidae, owing to its white colour and large size, detection of breeding pairs remained imperfect for each over several sampling occasions. However, because we repeated the sampling sessions, detection of swan pairs by the end of the monitoring period was as high as 0.94. These results are consistent with previous assertions that the mute swan is a species of high ecological plasticity, which may partly explain its recent colonization rates. Given that even swan breeding events were imperfectly detected on each occasion, we highlight the fact that most studies of breeding ducks (which are more cryptic) would be considerably improved by better considering detection biases.     

Productivity and Temperature as Drivers of Seasonal and Spatial Variations of Dissolved Methane in the Southern Bight of the North Sea

Dissolved CH₄ concentrations in the Belgian coastal zone (North Sea) ranged between 670 nmol l^?1 nearshore and 4 nmol l^?1 offshore. Spatial variations of CH₄ were related to sediment organic matter (OM) content and gassy sediments. In nearshore stations with fine sand or muddy sediments, the CH₄ seasonal cycle followed water temperature, suggesting methanogenesis control by temperature in these OM-rich sediments. In offshore stations with permeable sediments, the CH₄ seasonal cycle showed a yearly peak following the chlorophyll-a spring peak, suggesting that in these OM-poor sediments, methanogenesis depended on freshly produced OM delivery. This does not exclude the possibility that some CH₄ might originate from dimethylsulfide (DMS) or dimethylsulfoniopropionate (DMSP) or methylphosphonate transformations in the most offshore stations. Yet, the average seasonal CH₄ cycle was unrelated to those of DMS(P), very abundant during the Phaeocystis bloom. The annual average CH₄ emission was 126 mmol m^?2 y^?1 in the most nearshore stations (~4 km from the coast) and 28 mmol m^?2 y^?1 in the most offshore stations (~23 km from the coast), 1260–280 times higher than the open ocean average value (0.1 mmol m^?2 y^?1). The strong control of CH₄ by sediment OM content and by temperature suggests that marine coastal CH₄ emissions, in particular in shallow areas, should respond to future eutrophication and warming of climate. This is supported by the comparison of CH₄ concentrations at five stations obtained in March 1990 and 2016, showing a decreasing trend consistent with alleviation of eutrophication in the area.     

Anastomosis is required for virulence of the fungal necrotroph Alternaria brassicicola

A fungal mycelium is typically composed of radially extending hyphal filaments interconnected by bridges created through anastomoses. These bridges facilitate the dissemination of nutrients, water, and signaling molecules throughout the colony. In this study, we used targeted gene deletion and nitrate utilization mutants of the cruciferous pathogen Alternaria brassicicola and two closely related species to investigate hyphal fusion (anastomosis) and its role in the ability of fungi to cause disease. All eight of the A. brassicicola isolates tested, as well as A. mimicula and A. japonica, were capable of self-fusion, with two isolates of A. brassicicola being capable of non-self-fusion. Disruption of the anastomosis gene homolog (Aso1) in A. brassicicola resulted in both the loss of self-anastomosis and pathogenicity on cabbage. This finding, combined with our discovery that a previously described nonpathogenic A. brassicicola mutant defective for a mitogen-activated protein kinase gene (amk1) also lacked the capacity for self-anastomosis, suggests that self-anastomosis is associated with pathogenicity in A. brassicicola.     

Active genes in junk DNA? Characterization of DUX genes embedded within 3.3 kb repeated elements

The human genome contains hundreds of repeats of the 3.3 kb family in regions associated with heterochromatin. We have previously isolated a 3.3 kb-like cDNA encoding a double homeodomain protein (DUX1). Demonstration that the protein was expressed in human rhabdomyosarcoma TE671 cells, and characterization of a homologous promoter suggested that functional DUX genes might be present in 3.3 kb elements. In the present study, we describe two nearly identical 3.3 kb/DUX genes derived from PAC 137F16 (DUX3), and TE671 genomic DNA (DUX5), both mapping to all the acrocentric chromosomes. Their promoters harbor a GC and a TATAA box, and the open reading frame of the intronless structural part encodes two DUX proteins differing by alternative translation initiation. The shorter protein of the DUX5 gene is identical to DUX1. Using a protein truncation test, we could show that these two proteins are encoded by total RNA, but not by poly (A)(+) RNA, from different human tissues and cell lines. Our results indicate that active genes of unusual structure are present in chromosome regions characterized by large amounts of heterochromatic repetitive DNA.