PICH regulates the abundance and localization of SUMOylated proteins on mitotic chromosomes

Proper chromosome segregation is essential for faithful cell division and if not maintained results in defective cell function caused by the abnormal distribution of genetic information. Polo-like kinase 1–interacting checkpoint helicase (PICH) is a DNA translocase essential for chromosome bridge resolution during mitosis. Its function in resolving chromosome bridges requires both DNA translocase activity and ability to bind chromosomal proteins modified by the small ubiquitin-like modifier (SUMO). However, it is unclear how these activities cooperate to resolve chromosome bridges. Here, we show that PICH specifically disperses SUMO2/3 foci on mitotic chromosomes. This PICH function is apparent toward SUMOylated topoisomerase IIα (TopoIIα) after inhibition of TopoIIα by ICRF-193. Conditional depletion of PICH using the auxin-inducible degron (AID) system resulted in the retention of SUMO2/3-modified chromosomal proteins, including TopoIIα, indicating that PICH functions to reduce the association of these proteins with chromosomes. Replacement of PICH with its translocase-deficient mutants led to increased SUMO2/3 foci on chromosomes, suggesting that the reduction of SUMO2/3 foci requires the remodeling activity of PICH. In vitro assays showed that PICH specifically attenuates SUMOylated TopoIIα activity using its SUMO-binding ability. Taking the results together, we propose a novel function of PICH in remodeling SUMOylated proteins to ensure faithful chromosome segregation.     

Arabidopsis Raf‐like kinases act as positive regulators of subclass III SnRK2 in osmostress signaling

Given their sessile nature, land plants must use various mechanisms to manage dehydration under water‐deficit conditions. Osmostress‐induced activation of the SNF1‐related protein kinase 2 (SnRK2) family elicits physiological responses such as stomatal closure to protect plants during drought conditions. With the plant hormone ABA receptors [PYR (pyrabactin resistance)/PYL (pyrabactin resistance‐like)/RCAR (regulatory component of ABA receptors) proteins] and group A protein phosphatases, subclass III SnRK2 also constitutes a core signaling module for ABA, and osmostress triggers ABA accumulation. How SnRK2 is activated through ABA has been clarified, although its activation through osmostress remains unclear. Here, we show that Arabidopsis ABA and abiotic stress‐responsive Raf‐like kinases (AtARKs) of the B3 clade of the mitogen‐activated kinase kinase kinase (MAPKKK) family are crucial in SnRK2‐mediated osmostress responses. Disruption of AtARKs in Arabidopsis results in increased water loss from detached leaves because of impaired stomatal closure in response to osmostress. Our findings obtained in vitro and in planta have shown that AtARKs interact physically with SRK2E, a core factor for stomatal closure in response to drought. Furthermore, we show that AtARK phosphorylates S171 and S175 in the activation loop of SRK2E in vitro and that Atark mutants have defects in osmostress‐induced subclass III SnRK2 activity. Our findings identify a specific type of B3‐MAPKKKs as upstream kinases of subclass III SnRK2 in Arabidopsis. Taken together with earlier reports that ARK is an upstream kinase of SnRK2 in moss, an existing member of a basal land plant lineage, we propose that ARK/SnRK2 module is evolutionarily conserved across 400 million years of land plant evolution for conferring protection against drought.     

Automatic exposure control at MDCT based on the contrast-to-noise ratio: Theoretical background and phantom study

PurposeTo develop a new automatic exposure control (AEC) technique based on the contrast-to-noise ratio (CNR) and provide constant lesion detectability.MethodsLesion detectability is affected by factors such as image noise, lesion contrast, and lesion size. We performed ROC analysis to assess the relationship between the optimum CNR and the lesion diameter at various levels of lesion contrast. We then developed a CNR-based AEC algorithm based on lesion detectability. Using CNR- based AEC algorithm, we performed visual evaluation of low-contrast detectability by 5 radiologists on a low-contrast module of the Catphan phantom, a contrast-difference level of 1.0% (difference in the CT number = 10 HU), and objects 3.0–9.0 mm in diameter.ResultsOn step-and-shoot scans the mean detection fraction with CNR-based AEC remained almost constant from 88 to 99 % regardless of the lesion size. We observed the same trend on helical scans, the mean detection fraction with CNR-based AEC exhibited a high score from 91 to 100%. Although CNR-based AEC maintains higher CNR for smaller size or lower contrast lesion, radiation dose on 3 mm lesion resulted in about 13 times larger than that of 9 mm lesion size. CTDI_vol for the CNR-based AEC technique changed dramatically with the SD_Z from 7.5 to 100.0 mGy for step-and-shoot scans and from 9.1 to 121.5 mGy for helical scans.ConclusionsFrom the viewpoint of ROC analysis-based CNR for lesion detection, CNR-based AEC potentially provide image quality advantages for clinical implementation.     

Chemical Conversion of Some Ribonucleosides into the Corresponding β-D-Arabinofuranosyl Derivatives1

Abstract

Five 3′,5′-di-O-acylribonucleosides were converted into the corresponding β-D-arabinofuranosyl derivatives through DMSO-oxidation followed by NaBH₄-reduction and deacylation with NaOMe-MeOH.     

Scolecenchelys fuscogularis (Anguilliformes: Ophichthidae, Myrophinae), a new worm eel from Japan

A new species of worm eel (Ophichthidae, subfamily Myrophinae), Scolecenchelys fuscogularis, is described from two specimens collected at 90–147 m depth off the coast of Japan. The new species is characterized by its dorsal-fin origin, which is located posterior to a vertical through the anus, its high total number of vertebrae (146–149), and its uniserial dentition on jaws and vomer. The new species is similar to Scolecenchelys australis and Scolecenchelys tasmaniensis in having 148–152 total and 60–61 preanal vertebrae and its uniserial teeth, but can be distinguished from the latter two species as it has a larger head [8.5–8.8 % of total length (TL) vs. 7.8–8.3 %], a longer trunk (39 % TL vs. 34–35 %), and a shorter tail (52–53 % TL vs. 56–58 %). Although S. fuscogularis most resembles Scolecenchelys chilensis in having 146–159 total and 59–64 preanal vertebrae and uniserial teeth, as well as in the proportions of the head, trunk and tail, the new species differs from the latter in having a smaller head (8.5–8.8 % TL vs. 8.9–9.7 %), a more slender body (body depth 1.5–1.6 % TL vs. 2.3–2.9 %), a more posterior dorsal-fin origin (horizontal distance between the origin and a vertical through the anus 83 % of head length vs. 36–54 %), no groove on the ventral side of its snout, and a dark lower jaw with a patch of melanophores on the ventral side of its branchial basket.     

Effects of remnant primary forests on ant and dung beetle species diversity in a secondary forest in Sarawak, Malaysia

Tropical landscape structures have been transformed into mosaic structures consisting of small patches of primary and secondary forests, and areas of other land use. Diversity of insect assemblages is often higher in primary forests than in surrounding secondary forests. However, little is known about how the primary forests affect diversity in surrounding secondary forests in a landscape. In Sarawak, Malaysia, the typical landscape in areas from which lowland tropical rainforests had originally spread consists mainly of primary and secondary forests, with small areas of cultivation. In this study, we examined how the proportion of remnant primary forests in a landscape affects species diversity and species composition of ants and dung beetles in Macaranga-dominated secondary forests. The proportions were quantified based on remote-sensing data at various spatial scales, ranging from 100- to 5,000-m radius from each of the target forests. We found that the proportions of remnant primary forests within a 100-m radius had a significant positive effect on ant species diversity, and those within 100-, 300-, and 500-m radii significantly affected species compositions. However, the proportions of remnant primary forests had no significant relationship with dung beetle diversity, while those within 100- and 1,000-m radii had significant effects on species composition. The different responses to the remnant primary forests are likely to be related to differences in the movement and dispersal traits between the two taxa.     

TGFβs Modulate Permeability of the Blood-Epididymis Barrier in an In Vitro Model

The blood-epididymis barrier (BEB) is formed by epithelial tight junctions mediating selective permeability of the epididymal epithelium. Defective barrier function can disturb the balance of the epididymal milieu, which may result in infertility. The stroma of the epididymis contains high amounts of cytokines of the TGFβ family of unknown function. We screened possible effects of all three TGFβ isoforms on paracellular tightness in a BEB in vitro model based on the strongly polarized mouse epididymal epithelial MEPC5 cells in the transwell system. In this model we found a robust transepithelial electrical resistance (TER) of about 840 Ω x cm². Effects on the paracellular permeability were evaluated by two methods, TER and FITC-Dextran-based tracer diffusion assays. Both assays add up to corresponding results indicating a time-dependent disturbance of the BEB differentially for the three TGFβ isoforms (TGFβ3>TGFβ1>TGFβ2) in a TGFβ-recetor-1 kinase- and Smad-dependent manner. The tight junction protein claudin-1 was found to be reduced by the treatment with TGFβs, whereas occludin was not influenced. Epididymal epithelial cells are predominantly responsive to TGFβs from the basolateral side, suggesting that TGFβ may have an impact on the epididymal epithelium from the stroma in vivo. Our data show for the first time that TGFβs decrease paracellular tightness in epididymal epithelial cells, thus establishing a novel mechanism of regulation of BEB permeability, which is elementary for sperm maturation and male fertility.     

Functional Analysis of Deep Intronic SNP rs13438494 in Intron 24 of PCLO Gene

The single nucleotide polymorphism (SNP) rs13438494 in intron 24 of PCLO was significantly associated with bipolar disorder in a meta-analysis of genome-wide association studies. In this study, we performed functional minigene analysis and bioinformatics prediction of splicing regulatory sequences to characterize the deep intronic SNP rs13438494. We constructed minigenes with A and C alleles containing exon 24, intron 24, and exon 25 of PCLO to assess the genetic effect of rs13438494 on splicing. We found that the C allele of rs13438494 reduces the splicing efficiency of the PCLO minigene. In addition, prediction analysis of enhancer/silencer motifs using the Human Splice Finder web tool indicated that rs13438494 induces the abrogation or creation of such binding sites. Our results indicate that rs13438494 alters splicing efficiency by creating or disrupting a splicing motif, which functions by binding of splicing regulatory proteins, and may ultimately result in bipolar disorder in affected people.     

Polymorphic mutations in mouse mitochondrial DNA regulate a tumor phenotype

To examine whether polymorphic mtDNA mutations that do not induce significant respiration defects regulate phenotypes of tumor cells, we used mouse transmitochondrial tumor cells (cybrids) with nuclear DNA from C57BL/6 (B6) strain and mtDNA from allogenic C3H strain. The results showed that polymorphic mutations of C3H mtDNA in the cybrids induced hypoxia sensitivity, resulting in a delay of tumor formation on their subcutaneous inoculation into B6 mice. Therefore, the effects of polymorphic mutations in normal mtDNA have to be carefully considered, particularly when we apply the gene therapy to the embryos to replace their pathogenic mtDNA by normal mtDNA.