Polycomb group proteins have an essential role in the epigenetic maintenance of repressive chromatin states. The gene-silencing activity of the Polycomb repressive complex 2 (PRC2) depends on its ...ability to trimethylate lysine 27 of histone H3 (H3K27) by the catalytic SET domain of the EZH2 subunit, and at least two other subunits of the complex: SUZ12 and EED. Here we show that the carboxy-terminal domain of EED specifically binds to histone tails carrying trimethyl-lysine residues associated with repressive chromatin marks, and that this leads to the allosteric activation of the methyltransferase activity of PRC2. Mutations in EED that prevent it from recognizing repressive trimethyl-lysine marks abolish the activation of PRC2 in vitro and, in Drosophila, reduce global methylation and disrupt development. These findings suggest a model for the propagation of the H3K27me3 mark that accounts for the maintenance of repressive chromatin domains and for the transmission of a histone modification from mother to daughter cells.
Animals undergo periods of behavioral quiescence and arousal in response to environmental, circadian, or developmental cues. During larval molts, C. elegans undergoes a period of profound behavioral ...quiescence termed lethargus. Locomotion quiescence during lethargus was abolished in mutants lacking a neuropeptide receptor (NPR-1) and was reduced in mutants lacking NPR-1 ligands (FLP-18 and FLP-21). Wild-type strains are polymorphic for the npr-1 gene, and their lethargus behavior varies correspondingly. Locomotion quiescence and arousal were mediated by decreased and increased secretion of an arousal neuropeptide (PDF-1) from central neurons. PDF receptors (PDFR-1) expressed in peripheral mechanosensory neurons enhanced touch-evoked calcium transients. Thus, a central circuit stimulates arousal from lethargus by enhancing the sensitivity of peripheral mechanosensory neurons in the body. These results define a circuit mechanism controlling a developmentally programmed form of quiescence.
•NPR-1 and its ligands are required for locomotion quiescence during lethargus•Increased activity in the RMG circuit promotes locomotion arousal•Arousal is mediated by increased secretion of PDF-1 from the RMG circuit•PDF-1 enhances the sensitivity of mechanosory neurons, increasing motility
C. elegans exhibits a profound behavioral quiescence during larval molts. Choi et al. show that locomotion quiescence and arousal are mediated by decreased and increased secretion of PDF-1 from a central circuit. PDF-1 enhances motility by increasing the sensitivity of peripheral mechanosensory neurons.
C9ORF78 is a poorly characterized protein found in diverse eukaryotes. Previous work indicated overexpression of C9ORF78 in malignant tissues indicating a possible involvement in growth regulatory ...pathways. Additional studies in fission yeast and humans uncover a potential function in regulating the spliceosome. In studies of GFP-tagged C9ORF78 we observed a dramatic reduction in protein abundance in cells grown to confluence and/or deprived of serum growth factors. Serum stimulation induced synchronous re-expression of the protein in HeLa cells. This effect was also observed with the endogenous protein. Overexpressing either E2F1 or N-Myc resulted in elevated C9ORF78 expression potentially explaining the serum-dependent upregulation of the protein. Immunofluorescence analysis indicates that C9ORF78 localizes to nuclei in interphase but does not appear to concentrate in speckles as would be expected for a splicing protein. Surprisingly, a subpopulation of C9ORF78 co-localizes with ACA, Mad1 and Ndc80 in mitotic cells suggesting that this protein associates with kinetochores or centromeres. Levels of C9ORF78 at the centromere/kinetochore also increased upon activation of the mitotic checkpoint. Furthermore, knocking-down C9ORF78 caused mitotic defects. These studies uncover novel mitotic function and subcellular localization of C9ORF78.
Summary: C9ORF78 regulates chromosome segregation.
p53 is a well-established critical cell cycle regulator. By inducing transcription of the gene encoding p21, p53 inhibits cyclin-dependent kinase (CDK)-mediated phosphorylation of cell cycle ...inhibitor retinoblastoma (RB) proteins. Phosphorylation of RB releases E2F transcription factor proteins that transactivate cell cycle–promoting genes. Here, we sought to uncover the contribution of p53, p21, CDK, RB, and E2F to the regulation of ferroptosis, an oxidative form of cell death. Our studies have uncovered unexpected complexity in this regulation. First, we showed that elevated levels of p53 enhance ferroptosis in multiple inducible and isogenic systems. On the other hand, we found that p21 suppresses ferroptosis. Elevation of CDK activity also suppressed ferroptosis under conditions where p21 suppressed ferroptosis, suggesting that the impact of p21 must extend beyond CDK inhibition. Furthermore, we showed that overexpression of E2F suppresses ferroptosis in part via a p21-dependent mechanism, consistent with reports that this transcription factor can induce transcription of p21. Finally, deletion of RB genes enhanced ferroptosis. Taken together, these results show that signals affecting ferroptotic sensitivity emanate from multiple points within the p53 tumor suppressor pathway.
Tropical forests dominate global terrestrial carbon (C) exchange, and recent droughts in the Amazon Basin have contributed to short‐term declines in terrestrial carbon dioxide uptake and storage. ...However, the effects of longer‐term climate variability on tropical forest carbon dynamics are still not well understood. We synthesised field data from more than 150 tropical forest sites to explore how climate regulates tropical forest aboveground net primary productivity (ANPP) and organic matter decomposition, and combined those data with two existing databases to explore climate – C relationships globally. While previous analyses have focused on the effects of either temperature or rainfall on ANPP, our results highlight the importance of interactions between temperature and rainfall on the C cycle. In cool forests (< 20 °C), high rainfall slowed rates of C cycling, but in warm tropical forests (> 20 °C) it consistently enhanced both ANPP and decomposition. At the global scale, our analysis showed an increase in ANPP with rainfall in relatively warm sites, inconsistent with declines in ANPP with rainfall reported previously. Overall, our results alter our understanding of climate – C cycle relationships, with high precipitation accelerating rates of C exchange with the atmosphere in the most productive biome on earth.
Videofluoroscopy has been shown to provide essential information in the evaluation of the functionality of total knee arthroplasties. However, due to the limitation in the field of view, most systems ...can only assess knee kinematics during highly restricted movements. To avoid the limitations of a static image intensifier, a moving fluoroscope has been presented as a standalone system that allows tracking of the knee during multiple complete cycles of level- and downhill-walking, as well as stair descent, in combination with the synchronous assessment of ground reaction forces and whole body skin marker measurements. Here, we assess the ability of the system to keep the knee in the field of view of the image intensifier. By measuring ten total knee arthroplasty subjects, we demonstrate that it is possible to maintain the knee to within 1.8 ± 1.4 cm vertically and 4.0 ± 2.6 cm horizontally of the centre of the intensifier throughout full cycles of activities of daily living. Since control of the system is based on real-time feedback of a wire sensor, the system is not dependent on repeatable gait patterns, but is rather able to capture pathological motion patterns with low inter-trial repeatability.
Although the relevance of understanding spinal kinematics during functional activities in patients with complex spinal deformities is undisputed among researchers and clinicians, evidence using skin ...marker-based motion capture systems is still limited to a handful of studies, mostly conducted on healthy subjects and using non-validated marker configurations. The current study therefore aimed to explore the validity of a previously developed enhanced trunk marker set for the static measurement of spinal curvature angles in patients with main thoracic adolescent idiopathic scoliosis. In addition, the impact of inaccurate marker placement on curvature angle calculation was investigated.
Ten patients (Cobb angle: 44.4±17.7 degrees) were equipped with radio-opaque markers on selected spinous processes and underwent a standard biplanar radiographic examination. Subsequently, radio-opaque markers were replaced with retro-reflective markers and the patients were measured statically using a Vicon motion capture system. Thoracolumbar/lumbar and thoracic curvature angles in the sagittal and frontal planes were calculated based on the centers of area of the vertebral bodies and radio-opaque markers as well as the three-dimensional position of the retro-reflective markers. To investigate curvature angle estimation accuracy, linear regression analyses among the respective parameters were used. The impact of inaccurate marker placement was explored using linear regression analyses among the radio-opaque marker- and spinous process-derived curvature angles.
The results demonstrate that curvatures angles in the sagittal plane can be measured with reasonable accuracy, whereas in the frontal plane, angles were systematically underestimated, mainly due to the positional and structural deformities of the scoliotic vertebrae. Inaccuracy of marker placement had a greater impact on thoracolumbar/lumbar than thoracic curvature angles. It is suggested that spinal curvature measurements are included in marker-based clinical gait analysis protocols in order to enable a deeper understanding of the biomechanical behavior of the healthy and pathological spine in dynamic situations as well as to comprehensively evaluate treatment effects.
Global changes such as variations in plant net primary production are likely to drive shifts in leaf litterfall inputs to forest soils, but the effects of such changes on soil carbon (C) cycling and ...storage remain largely unknown, especially in C‐rich tropical forest ecosystems. We initiated a leaf litterfall manipulation experiment in a tropical rain forest in Costa Rica to test the sensitivity of surface soil C pools and fluxes to different litter inputs. After only 2 years of treatment, doubling litterfall inputs increased surface soil C concentrations by 31%, removing litter from the forest floor drove a 26% reduction over the same time period, and these changes in soil C concentrations were associated with variations in dissolved organic matter fluxes, fine root biomass, microbial biomass, soil moisture, and nutrient fluxes. However, the litter manipulations had only small effects on soil organic C (SOC) chemistry, suggesting that changes in C cycling, nutrient cycling, and microbial processes in response to litter manipulation reflect shifts in the quantity rather than quality of SOC. The manipulation also affected soil CO ₂ fluxes; the relative decline in CO ₂ production was greater in the litter removal plots (−22%) than the increase in the litter addition plots (+15%). Our analysis showed that variations in CO ₂ fluxes were strongly correlated with microbial biomass pools, soil C and nitrogen (N) pools, soil inorganic P fluxes, dissolved organic C fluxes, and fine root biomass. Together, our data suggest that shifts in leaf litter inputs in response to localized human disturbances and global environmental change could have rapid and important consequences for belowground C storage and fluxes in tropical rain forests, and highlight differences between tropical and temperate ecosystems, where belowground C cycling responses to changes in litterfall are generally slower and more subtle.
OTSSP167 was recently characterized as a potent inhibitor for maternal embryonic leucine zipper kinase (MELK) and is currently tested in Phase I clinical trials for solid tumors that have not ...responded to other treatment. Here we report that OTSSP167 abrogates the mitotic checkpoint at concentrations used to inhibit MELK. The abrogation is not recapitulated by RNAi mediated silencing of MELK in cells. Although OTSSP167 indeed inhibits MELK, it exhibits off-target activity against Aurora B kinase in vitro and in cells. Furthermore, OTSSP167 inhibits BUB1 and Haspin kinases, reducing phosphorylation at histones H2AT120 and H3T3 and causing mislocalization of Aurora B and associated chromosomal passenger complex from the centromere/kinetochore. The results suggest that OTSSP167 may have additional mechanisms of action for cancer cell killing and caution the use of OTSSP167 as a MELK specific kinase inhibitor in biochemical and cellular assays.
Early detection improves hepatocellular carcinoma (HCC) outcomes, but better noninvasive surveillance tools are needed. We aimed to identify and validate methylated DNA markers (MDMs) for HCC ...detection. Reduced representation bisulfite sequencing was performed on DNA extracted from 18 HCC and 35 control tissues. Candidate MDMs were confirmed by quantitative methylation‐specific PCR in DNA from independent tissues (74 HCC, 29 controls). A phase I plasma pilot incorporated quantitative allele‐specific real‐time target and signal amplification assays on independent plasma‐extracted DNA from 21 HCC cases and 30 controls with cirrhosis. A phase II plasma study was then performed in 95 HCC cases, 51 controls with cirrhosis, and 98 healthy controls using target enrichment long‐probe quantitative amplified signal (TELQAS) assays. Recursive partitioning identified best MDM combinations. The entire MDM panel was statistically cross‐validated by randomly splitting the data 2:1 for training and testing. Random forest (rForest) regression models performed on the training set predicted disease status in the testing set; median areas under the receiver operating characteristics curve (AUCs; and 95% confidence interval CI) were reported after 500 iterations. In phase II, a six‐marker MDM panel (homeobox A1 HOXA1, empty spiracles homeobox 1 EMX1, AK055957, endothelin‐converting enzyme 1 ECE1, phosphofructokinase PFKP, and C‐type lectin domain containing 11A CLEC11A) normalized by beta‐1,3‐galactosyltransferase 6 (B3GALT6) level yielded a best‐fit AUC of 0.96 (95% CI, 0.93‐0.99) with HCC sensitivity of 95% (88%‐98%) at specificity of 92% (86%‐96%). The panel detected 3 of 4 (75%) stage 0, 39 of 42 (93%) stage A, 13 of 14 (93%) stage B, 28 of 28 (100%) stage C, and 7 of 7 (100%) stage D HCCs. The AUC value for alpha‐fetoprotein (AFP) was 0.80 (0.74‐0.87) compared to 0.94 (0.9‐0.97) for the cross‐validated MDM panel (P < 0.0001). Conclusion: MDMs identified in this study proved to accurately detect HCC by plasma testing. Further optimization and clinical testing of this promising approach are indicated.
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