Rad54B serves as a scaffold in the DNA damage response that limits checkpoint strength

The strength of the DNA damage checkpoint critically influences cell fate, yet the mechanisms behind the fine tuning of checkpoint strength during the DNA damage response (DDR) are poorly understood. Here we show that ​Rad54B—a SNF2 helicase-like DNA-repair protein—limits the strength of both the G1/S and G2/M checkpoints. We find that ​Rad54B functions as a scaffold for ​p53 degradation via its direct interaction with the ​MDM2–​MDMX ubiquitin–ligase complex. During the early phases of the DDR, ​Rad54B is upregulated, thereby maintaining low checkpoint strength and facilitating cell cycle progression. Once the ​p53-mediated checkpoint is established, ​Rad54B is downregulated, and high checkpoint strength is maintained. Constitutive upregulation of ​Rad54B activity, which is frequently observed in tumours, promotes genomic instability because of checkpoint override. Thus, the scaffolding function of ​Rad54B dynamically regulates the maintenance of genome integrity by limiting checkpoint strength.UTokyo Research掲載「がん発生の基盤となる仕組みを探る」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/discovery-of-a-basic-mechanism-of-cancer-development/UTokyo Research "Discovery of a basic mechanism of cancer development" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/discovery-of-a-basic-mechanism-of-cancer-development

Expression of the wilms' tumor gene WT1 in human malignant mesothelioma cell lines and relationship to platelet‐derived growth factor A and insulin‐like growth factor 2 expression

Mutations in the WT1 tumor suppressor gene are known to contribute to the development of Wilms' tumor (WT) and associated gonadal abnormalities. WT1 is expressed principally in the fetal kidney, developing gonads, and spleen and also in the mesothelium, which lines the coelomic cavities. These tissues develop from mesenchymal components that have subsequently become epithelialized, and it has therefore been proposed that WT1 may play a role in this transition of cell types. To test the possible involvement of this gene in malignant mesothelioma, we have first studied its expression in a panel of human normal and malignant mesothelial cell lines. WT1 mRNA expression levels varied greatly between the cell lines and no specific chromosomal aberration on 11p, which could be related to the variation in WT1 expression in these cell lines, was observed. Furthermore, no gross deletions, rearrangements, or functionally inactivating point mutations in the WT1 coding region were identified. All four WT1 splice variants were observed at similar levels in these cell lines. The WT1 gene encodes a zinc‐finger transcription factor and the four protein isoforms are each believed to act as transcriptional repressors of certain growth factor genes. Lack of WT1 expression is thus predicted to result in growth stimulation of tumor cells. Binding of one particular WT1 isoform construct to the insulin‐like growth factor 2 (IGF2) and platelet‐derived growth factor A (PDGFA) gene promoters has been demonstrated to result in repression of these genes in transient transfection studies. Analysis of IGF2 and PDGFA mRNA expression levels compared with WT1 mRNA expression levels failed to demonstrate an inverse correlation in the mesothelial cell lines, which endogenously express these genes. Finally, the putative role of WT1 in the transition of cell types was investigated. No obvious correlation between WT1 expression levels and cell morphology of the malignant mesothelial cell lines was evident from this study. Moreover, no change in WT1 expression was observed in normal mesothelial cells which were, by alteration of culture conditions, manipulated to switch from the mesenchymal to epithelial morphology.</p

Integral transform of MHD flow with heat and mass transfer of a biofluid in a parallel plate channel / Transformação integral do escoamento MHD com transferência de calor e massa de um biofluido em um canal de placa paralela

Foi estudado o escoamento transiente pulsátil através de um canal poroso do tipo Darcy-Forchheimer de um biofluido influenciado por um campo magnético externo aplicado transversalmente ao canal com reação química. Na formulação matemática foi considerado o escoamento laminar, bidimensional, incompressível de um fluido eletricamente condutor, através de um meio poroso, dentro de um canal formado entre placas planas paralelas com transpiração da parede. Os campos de velocidade, concentração e temperatura foram solucionados utilizando a Técnica da Transformada Integral Generalizada (GITT) e foi realizada uma análise de convergência das expansões em série, obtendo convergências satisfatórias com poucos termos nos somatórios. As soluções obtidas foram comparadas com as da literatura obtendo-se uma boa concordância em todos os campos e situações estudadas. Foi avaliada ainda a influência do número de Reynolds, do número de Prandtl, do número de Schmidt e do parâmetro magnético nos perfis de velocidade, temperatura e concentração, observando-se que o escoamento é fortemente sensível aos efeitos do número de Reynolds e do parâmetro magnético. Uma análise transiente também foi realizada observando que devido ao fluido estar em repouso no início, ele não é imediatamente acelerado, gerando um retardo no perfil de velocidade para tempos pequenos. 

Stimulation of Dmc1-mediated DNA strand exchange by the human Rad54B protein

The process of homologous recombination is indispensable for both meiotic and mitotic cell division, and is one of the major pathways for double-strand break (DSB) repair. The human Rad54B protein, which belongs to the SWI2/SNF2 protein family, plays a role in homologous recombination, and may function with the Dmc1 recombinase, a meiosis-specific Rad51 homolog. In the present study, we found that Rad54B enhanced the DNA strand-exchange activity of Dmc1 by stabilizing the Dmc1–single-stranded DNA (ssDNA) complex. Therefore, Rad54B may stimulate the Dmc1-mediated DNA strand exchange by stabilizing the nucleoprotein filament, which is formed on the ssDNA tails produced at DSB sites during homologous recombination

The whole blood transcriptional regulation landscape in 465 COVID-19 infected samples from Japan COVID-19 Task Force

「コロナ制圧タスクフォース」COVID-19患者由来の血液細胞における遺伝子発現の網羅的解析 --重症度に応じた遺伝子発現の変化には、ヒトゲノム配列の個人差が影響する--. 京都大学プレスリリース. 2022-08-23.Coronavirus disease 2019 (COVID-19) is a recently-emerged infectious disease that has caused millions of deaths, where comprehensive understanding of disease mechanisms is still unestablished. In particular, studies of gene expression dynamics and regulation landscape in COVID-19 infected individuals are limited. Here, we report on a thorough analysis of whole blood RNA-seq data from 465 genotyped samples from the Japan COVID-19 Task Force, including 359 severe and 106 non-severe COVID-19 cases. We discover 1169 putative causal expression quantitative trait loci (eQTLs) including 34 possible colocalizations with biobank fine-mapping results of hematopoietic traits in a Japanese population, 1549 putative causal splice QTLs (sQTLs; e.g. two independent sQTLs at TOR1AIP1), as well as biologically interpretable trans-eQTL examples (e.g., REST and STING1), all fine-mapped at single variant resolution. We perform differential gene expression analysis to elucidate 198 genes with increased expression in severe COVID-19 cases and enriched for innate immune-related functions. Finally, we evaluate the limited but non-zero effect of COVID-19 phenotype on eQTL discovery, and highlight the presence of COVID-19 severity-interaction eQTLs (ieQTLs; e.g., CLEC4C and MYBL2). Our study provides a comprehensive catalog of whole blood regulatory variants in Japanese, as well as a reference for transcriptional landscapes in response to COVID-19 infection

DOCK2 is involved in the host genetics and biology of severe COVID-19

「コロナ制圧タスクフォース」COVID-19疾患感受性遺伝子DOCK2の重症化機序を解明 --アジア最大のバイオレポジトリーでCOVID-19の治療標的を発見--. 京都大学プレスリリース. 2022-08-10.Identifying the host genetic factors underlying severe COVID-19 is an emerging challenge. Here we conducted a genome-wide association study (GWAS) involving 2, 393 cases of COVID-19 in a cohort of Japanese individuals collected during the initial waves of the pandemic, with 3, 289 unaffected controls. We identified a variant on chromosome 5 at 5q35 (rs60200309-A), close to the dedicator of cytokinesis 2 gene (DOCK2), which was associated with severe COVID-19 in patients less than 65 years of age. This risk allele was prevalent in East Asian individuals but rare in Europeans, highlighting the value of genome-wide association studies in non-European populations. RNA-sequencing analysis of 473 bulk peripheral blood samples identified decreased expression of DOCK2 associated with the risk allele in these younger patients. DOCK2 expression was suppressed in patients with severe cases of COVID-19. Single-cell RNA-sequencing analysis (n = 61 individuals) identified cell-type-specific downregulation of DOCK2 and a COVID-19-specific decreasing effect of the risk allele on DOCK2 expression in non-classical monocytes. Immunohistochemistry of lung specimens from patients with severe COVID-19 pneumonia showed suppressed DOCK2 expression. Moreover, inhibition of DOCK2 function with CPYPP increased the severity of pneumonia in a Syrian hamster model of SARS-CoV-2 infection, characterized by weight loss, lung oedema, enhanced viral loads, impaired macrophage recruitment and dysregulated type I interferon responses. We conclude that DOCK2 has an important role in the host immune response to SARS-CoV-2 infection and the development of severe COVID-19, and could be further explored as a potential biomarker and/or therapeutic target