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Naïve B cells become activated and differentiate into antibody‐secreting plasma cells (PCs) when encountering antigens. Here, we reveal that the WW domain‐containing adapter protein with coiled‐coil (Wac), which is important for histone H2B ubiquitination (ubH2B), is essential for PC differentiation. We demonstrate that B cell‐specific Wac knockout mice have severely compromised T cell‐dependent and ‐independent antibody responses. PC differentiation is drastically compromised despite undisturbed germinal center B cell response in the mutant mice. We also observe a significant reduction in global ubH2B in Wac‐deficient B cells, which is correlated with downregulated expression of some genes critical for cell metabolism. Thus, our findings demonstrate an essential role of Wac‐mediated ubH2B in PC differentiation and shed light on the epigenetic mechanisms underlying this process. [ABSTRACT FROM AUTHOR]

Asymmetric cell division (ACD) produces morphologically and behaviorally distinct cells and is the primary way to generate cell diversity. In the model bacterium Caulobacter crescentus, the polarization of distinct scaffold-signaling hubs at the swarmer and stalked cell poles constitutes the basis of ACD. However, mechanisms involved in the formation of these hubs remain elusive. Here, we show that a swarmer-cell-pole scaffold, PodJ, forms biomolecular condensates both in vitro and in living cells via phase separation. The coiled-coil 4–6 and the intrinsically disordered regions are the primary domains that contribute to biomolecular condensate generation and signaling protein recruitment in PodJ. Moreover, a negative regulation of PodJ phase separation by the stalked-cell-pole scaffold protein SpmX is revealed. SpmX impedes PodJ cell-pole accumulation and affects its recruitment ability. Together, by modulating the assembly and dynamics of scaffold-signaling hubs, phase separation may serve as a general biophysical mechanism that underlies the regulation of ACD in bacteria and other organisms. The polarization of distinct scaffold-signaling hubs at opposite cell poles constitutes the basis of asymmetric cell division. Here, the authors show that phase separation serves as a general mechanism to regulate the assembly and dynamics of a new-pole scaffold-signaling hub. [ABSTRACT FROM AUTHOR]

The 5-methylcytosine (m5C) modification on an mRNA molecule is deposited by Nsun2 and its paralog Nsun6. While the physiological functions of Nsun2 have been carefully studied using gene knockout (KO) mice, the physiological functions of Nsun6 remain elusive. In this study, we generated an Nsun6-KO mouse strain, which exhibited no apparent phenotype in both the development and adult stages as compared to wild-type mice. Taking advantage of this mouse strain, we identified 80 high-confident Nsun6-dependent m5C sites by mRNA bisulfite sequencing in five different tissues and systematically analyzed the transcriptomic phenotypes of Nsun6-KO tissues by mRNA sequencing. Our data indicated that Nsun6 is not required for the homeostasis of these organs under laboratory housing conditions, but its loss may affect immune response in the spleen and oxidoreductive reaction in the liver under certain conditions. Additionally, we further investigated T-cell-dependent B cell activation in KO mice and found that Nsun6 is not essential for the germinal center B cell formation but is associated with the formation of antibody-secreting plasma cells. Finally, we found that Nsun6-mediated m5C modification does not have any evident influence on the stability of Nsun6 target mRNAs, suggesting that Nsun6-KO-induced phenotypes may be associated with other functions of the m5C modification or Nsun6 protein. [ABSTRACT FROM AUTHOR]

E-commerce platforms apply recommendation technology to a wide variety of commercial websites to help users quickly find the product they need from a large number of products. At present, recommendation systems have been widely used in large-scale e-commerce websites, and most e-commerce shopping websites attract customers through the image information of goods. In this paper, the research status of content-based image retrieval algorithms is analysed, and how to use image content information to recommend goods is studied. A hierarchical commodity classification and retrieval system are designed. A class decision layer is used to determine the category of commodity images and then precisely retrieve the corresponding category of commodity image features. The corresponding relationship between different commodity visual features is used to recommend commodities, and a matching recommendation algorithm for commodities is proposed. Experiments show that the proposed image content-based recommendation method can coordinate with features, and its recommendation results have high accuracy in practical applications. [ABSTRACT FROM AUTHOR]

Micro RNAs have been shown to play a role in B-cell differentiation and activation. Here, we found miR-182 to be highly induced in activated B cells. However, mice lacking miR-182 have normal B-cell and T-cell development. Interestingly, mutant mice exhibited a defective antibody response at early time-points in the immunization regimen when challenged with a T-cell-dependent antigen. Germinal centres were formed but the generation of extrafollicular plasma cells was defective in the spleens of immunized miR-182-deficient mice. Mutant mice were also not able to respond to a T-cell-independent type 2 antigen, which typically elicited an extrafollicular B-cell response. Taken together, the data indicated that miR-182 plays a critical role in driving extrafollicular B-cell antibody responses. [ABSTRACT FROM AUTHOR]

Adenosine deaminase acting on RNA-1 (ADAR1) is a ubiquitously expressed RNA deaminase catalyzing adenosine-to-inosine editing to prevent hyperactivated cytosolic double-stranded RNA (dsRNA) response mediated by MDA5. Here, we demonstrate that ADAR1 is essential for early B lymphopoiesis from late pro-B and large pre-B cell stages onward. ADAR1 exerts its requisite role via both MDA5-dependent and -independent pathways. Interestingly, the MDA5-dependent mechanisms regulate early pro-B to large pre-B cell transition by promoting early B cell survival. In contrast, the MDA5-independent mechanisms control large pre-B to small pre-B cell transition by regulating pre-B cell receptor (pre-BCR) expression. Moreover, we show that protein kinase R (PKR) and oligoadenylate synthetase/ribonuclease (OAS/RNase) L pathways are dispensable for ADAR1's role in early B lymphopoiesis. Importantly, we demonstrate that p150 isoform of ADAR1 exclusively accounts for ADAR1's function in early B lymphopoiesis, and its conventional dsRNA-binding, but not the Z-DNA/RNA-binding or the RNA-editing, activity is required for ADAR1's function in B cell development. Thus, our findings suggest that ADAR1 regulates early B lymphopoiesis through various mechanisms. [Display omitted] • ADAR1 p150 isoform, but not p110 isoform, is essential for early B lymphopoiesis • ADAR1 regulates pro-B to large pre-B cell transition in an MDA5-dependent manner • ADAR1 regulates pre-BCR expression to control large to small pre-B cell transition • The dsRNA-binding activity is required for ADAR1's function in early B lymphopoiesis Chen et al. report that the p150 isoform, but not p110 isoform, of RNA-editing enzyme ADAR1 is essential for B cell development. ADAR1 p150 exerts critical roles at various stages of early B cell development through its dsRNA-binding, but not Z-DNA/RNA-binding or RNA-editing, activity. [ABSTRACT FROM AUTHOR]

Stimulation of TLR7/9 by their respective ligands leads to the activation of IκB kinase α (IKKα) and Interferon Regulatory Factor 1 (IRF-1) and results in interferon (IFN)-β production in conventional dendritic cells (cDC). However, which other signaling molecules are involved in IKKα and IRF-1 activation during TLR7/9 signaling pathway are not known. We and others have shown that Bruton's Tyrosine Kinase (BTK) played a part in TLR9-mediated cytokine production in B cells and macrophages. However, it is unclear if BTK participates in TLR7/9-induced IFN-β production in cDC. In this study, we show that BTK is required for IFN-β synthesis in cDC upon TLR7/9 stimulation and that stimulated BTK-deficient cDC are defective in the induction of IKKα/β phosphorylation and IRF-1 activation. In addition, we demonstrate that Protein Kinase C µ (PKCµ) is also required for TLR7/9-induced IRF-1 activation and IFN-β upregulation in cDC and acts downstream of BTK. Taken together, we have uncovered two new molecules, BTK and PKCµ, that are involved in TLR7/9-triggered IFN-β production in cDC. [ABSTRACT FROM AUTHOR]

Bacteriophage-encoded serine recombinases have great potential in genetic engineering but their catalytic mechanisms have not been adequately studied. Integration of φBT1 and φC31 via their attachment (att) sites is catalyzed by integrases of the large serine recombinase subtype. Both φBT1 and φC31 integrases were found to cleave single-substrate att sites without synaptic complex formation, and φBT1 integrase relaxed supercoiled DNA containing a single integration site. Systematic mutation of the central att site dinucleotide revealed that cleavage was independent of nucleotide sequence, but rejoining was crucially dependent upon complementarity of the cleavage products. Recombination between att sites containing dinucleotides with antiparallel complementarity led to antiparallel recombination. Integrase-substrate pre-incubation experiments revealed that the enzyme can form an attP-integrase tetramer complex that then captures naked attB DNA, and suggested that two alternative assembly pathways can lead to synaptic complex formation. [ABSTRACT FROM PUBLISHER]

The spliceosome is a large ribonucleoprotein complex responsible for pre-mRNA splicing and genome stability maintenance. Disruption of the spliceosome activity may lead to developmental disorders and tumorigenesis. However, the physiological role that the spliceosome plays in B cell development and function is still poorly defined. Here, we demonstrate that ubiquitin-specific peptidase 39 (Usp39), a spliceosome component of the U4/U6.U5 tri-snRNP complex, is essential for B cell development. Ablation of Usp39 in B cell lineage blocks pre-pro-B to pro-B cell transition in the bone marrow, leading to a profound reduction of mature B cells in the periphery. We show that Usp39 specifically regulates immunoglobulin gene rearrangement in a spliceosome-dependent manner, which involves modulating chromatin interactions at the Igh locus. Moreover, our results indicate that Usp39 deletion reduces the pre-malignant B cells in Eμ-Myc transgenic mice and significantly improves their survival. [Display omitted] • Usp39 is essential for early B cell development in the bone marrow • Usp39 regulates immunoglobulin gene rearrangement in a spliceosome-dependent manner • Usp39 modulates chromatin interaction at the Igh locus • Deletion of Usp39 mitigates B cell lymphomagenesis in Eμ-Myc transgenic mice Ruan et al. report that the spliceosome component Usp39 is essential for B cell development by regulating immunoglobulin gene rearrangement. These results suggest that Usp39 could be a potential therapeutic target for B cell lymphomas [ABSTRACT FROM AUTHOR]

Tyrosine kinase c-Abl plays an important role in early B cell development. Its deletion leads to reduced pro- and pre-B cell generation in mice. However, its function in B cell terminal differentiation remains unexplored. Here, we used c-Ablf/f Aicdacre/+ mice, in which c-Abl is ablated only in antigen-activated B cells, to study the role of c-Abl in germinal center (GC) B and antibody-secreting plasma cell formation. Upon challenge with a model antigen, we found normal GC and memory B but reduced plasma cells and antigen-specific antibody response in the mutant mice. In-vitro studies revealed that plasma cells lacking c-Abl could be generated but did not accumulate in culture, indicative of survival defect. They also exhibited impaired STAT3 phosphorylation. The plasma cell defects could be rectified by introduction of Bim-deficiency or delivery of colivelin, a STAT3 activator, into c-Ablf/f Aicdacre/+ mice. Hence, c-Abl signalling regulates the survival of plasma cells. [ABSTRACT FROM AUTHOR]