SPDR-2 Histopathological investigation of the oligodendroglial tumors resected following alkylating agent chemotherapy

Oligodendrogliomas, i.e., lower grade gliomas with 1p/19q codeletion, are often responsive to chemotherapy, however, those tumors eventually recur and life-limiting in the majority of patients despite initial chemotherapeutic response. We have been treating those patients with upfront chemotherapy and subsequent resection following tumor volume decrease since 2006. This study aimed to elucidate the histological changes and the mechanism of recurrence after alkylating agent chemotherapy in oligodendrogliomas. Fifteen oligodendrogliomas (Grade 2: 12, Grade 3: 3) resected following tumor volume decrease after alkylating agent chemotherapy were included and compared with their pre-chemotherapy specimens. Histological changes were investigated using hematoxylin-eosin staining, and changes in proliferative activity, status of glioma stem cells (GSCs), and tumor-infiltrating macrophages were assessed using immunohistochemistry. The frequent histological findings following chemotherapy included a sparse glial background, abundant foamy cell infiltration, gliosis, calcification, and nuclear degradation. The Ki-67/MIB-1 index decreased and the number of macrophages increased after chemotherapy. Moreover, the ratio of GSCs to total tumor cells increased after chemotherapy. GSCs and macrophages constitute the mechanism of resistance to and recurrence after alkylating agent chemotherapy in oligodendrogliomas.

Zn2+-Dependent Nuclease Is Involved in Nuclear Degradation during the Programmed Cell Death of Secretory Cavity Formation in Citrus grandis ‘Tomentosa’ Fruits

Zn2+- and Ca2+-dependent nucleases exhibit activity toward dsDNA in the four classes of cation-dependent nucleases in plants. Programmed cell death (PCD) is involved in the degradation of cells during schizolysigenous secretory cavity formation in Citrus fruits. Recently, the Ca2+-dependent DNase CgCAN was proven to play a key role in nuclear DNA degradation during the PCD of secretory cavity formation in Citrus grandis ‘Tomentosa’ fruits. However, whether Zn2+-dependent nuclease plays a role in the PCD of secretory cells remains poorly understood. Here, we identified a Zn2+-dependent nuclease gene, CgENDO1, from Citrus grandis ‘Tomentosa’, the function of which was studied using Zn2+ ions cytochemical localization, DNase activity assays, in situ hybridization, and protein immunolocalization. The full-length cDNA of CgENDO1 contains an open reading frame of 906 bp that encodes a protein 301 amino acids in length with a S1/P1-like functional domain. CgENDO1 degrades linear double-stranded DNA at acidic and neutral pH. CgENDO1 is mainly expressed in the late stage of nuclear degradation of secretory cells. Further spatiotemporal expression patterns of CgENDO1 showed that CgENDO1 is initially located on the endoplasmic reticulum and then moves into intracellular vesicles and nuclei. During the late stage of nuclear degradation, it was concentrated in the area of nuclear degradation involved in nuclear DNA degradation. Our results suggest that the Zn2+-dependent nuclease CgENDO1 plays a direct role in the late degradation stage of the nuclear DNA in the PCD of secretory cavity cells of Citrus grandis ‘Tomentosa’ fruits.

Atg5 Regulates Selective Autophagy of the Parental Macronucleus during Tetrahymena Sexual Reproduction

Nuclear autophagy is an important selective autophagy process. The selective autophagy of sexual development micronuclei (MICs) and the programmed nuclear degradation of parental macronucleus (paMAC) occur during sexual reproduction in Tetrahymena thermophila. The molecular regulatory mechanism of nuclear selective autophagy is unclear. In this study, the autophagy-related protein Atg5 was identified from T. thermophila. Atg5 was localized in the cytoplasm in the early sexual-development stage and was localized in the paMAC in the late sexual-development stage. During this stage, the degradation of meiotic products of MIC was delayed in atg5i mutants. Furthermore, paMAC was abnormally enlarged and delayed or failed to degrade. The expression level and lipidation of Atg8.2 significantly decreased in the mutants. All these results indicated that Atg5 was involved in the regulation of the selective autophagy of paMAC by regulating Atg8.2 in Tetrahymena.

Rapid decay of host basal mRNAs during SARS-CoV-2 infection perturbs host antiviral mRNA biogenesis and export

A key feature of the mammalian innate immune response to viral infection is the transcriptional induction of interferon (IFN) genes, which encode for secreted proteins that prime the antiviral response and limit viral replication and dissemination. A hallmark of severe COVID-19 disease caused by SARS-CoV-2 is the low presence of IFN proteins in patient serum despite elevated levels of IFN-encoding mRNAs, indicative of post-transcriptional inhibition of IFN protein production. Herein, we show SARS-CoV-2 infection limits type I and type III IFN biogenesis by preventing the release of mRNA from their sites of transcription and/or triggering their nuclear degradation. In addition, SARS-CoV-2 infection inhibits nuclear-cytoplasmic transport of IFN mRNAs as a consequence of widespread cytosolic mRNA degradation mediated by both activation of the host antiviral endoribonuclease, RNase L, and by the SARS-CoV-2 protein, Nsp1. These findings argue that inhibition of host and/or viral Nsp1-mediated mRNA decay, as well as IFN treatments, may reduce viral-associated pathogenesis by promoting the innate immune response.

Perspective: Controlling Epidermal Terminal Differentiation with Transcriptional Bursting and RNA Bodies

The outer layer of the skin, the epidermis, is the principal barrier to the external environment: post-mitotic cells terminally differentiate to form a tough outer cornified layer of enucleate and flattened cells that confer the majority of skin barrier function. Nuclear degradation is required for correct cornified envelope formation. This process requires mRNA translation during the process of nuclear destruction. In this review and perspective, we address the biology of transcriptional bursting and the formation of ribonuclear particles in model organisms including mammals, and then examine the evidence that these phenomena occur as part of epidermal terminal differentiation.

Out or decay: fate determination of nuclear RNAs

In eukaryotes, RNAs newly synthesized by RNA polymerase II (RNAPII) undergo several processing steps prior to transport to the cytoplasm. It has long been known that RNAs with defects in processing or export are removed in the nucleus. Recent studies revealed that RNAs without apparent defects are also subjected to nuclear degradation, indicating that nuclear RNA fate is determined in a more complex and dynamic way than previously thought. Nuclear RNA sorting directly determines the quality and quantity of RNA pools for future translation and thus is of significant importance. In this essay, we will summarize recent studies on this topic, mainly focusing on findings in mammalian system, and discuss about important remaining questions and possible biological relevance for nuclear RNA fate determination.

The Tudor-domain protein TDRD7, mutated in congenital cataract, controls the heat shock protein HSPB1 (HSP27) and lens fiber cell morphology

Mutations of the RNA granule component TDRD7 (OMIM: 611258) cause pediatric cataract. We applied an integrated approach to uncover the molecular pathology of cataract in Tdrd7−/− mice. Early postnatal Tdrd7−/− animals precipitously develop cataract suggesting a global-level breakdown/misregulation of key cellular processes. High-throughput RNA sequencing integrated with iSyTE-bioinformatics analysis identified the molecular chaperone and cytoskeletal modulator, HSPB1, among high-priority downregulated candidates in Tdrd7−/− lens. A protein fluorescence two-dimensional difference in-gel electrophoresis (2D-DIGE)-coupled mass spectrometry screen also identified HSPB1 downregulation, offering independent support for its importance to Tdrd7−/− cataractogenesis. Lens fiber cells normally undergo nuclear degradation for transparency, posing a challenge: how is their cell morphology, also critical for transparency, controlled post-nuclear degradation? HSPB1 functions in cytoskeletal maintenance, and its reduction in Tdrd7−/− lens precedes cataract, suggesting cytoskeletal defects may contribute to Tdrd7−/− cataract. In agreement, scanning electron microscopy (SEM) revealed abnormal fiber cell morphology in Tdrd7−/− lenses. Further, abnormal phalloidin and wheat germ agglutinin (WGA) staining of Tdrd7−/− fiber cells, particularly those exhibiting nuclear degradation, reveals distinct regulatory mechanisms control F-actin cytoskeletal and/or membrane maintenance in post-organelle degradation maturation stage fiber cells. Indeed, RNA immunoprecipitation identified Hspb1 mRNA in wild-type lens lysate TDRD7-pulldowns, and single-molecule RNA imaging showed co-localization of TDRD7 protein with cytoplasmic Hspb1 mRNA in differentiating fiber cells, suggesting that TDRD7–ribonucleoprotein complexes may be involved in optimal buildup of key factors. Finally, Hspb1 knockdown in Xenopus causes eye/lens defects. Together, these data uncover TDRD7’s novel upstream role in elevation of stress-responsive chaperones for cytoskeletal maintenance in post-nuclear degradation lens fiber cells, perturbation of which causes early-onset cataracts.

Xao tam phan (Paramignya trimera) methanol extract induced apoptosis in hepatocellular carcinoma HepG2 cell line in vitro

Introduction: Xao Tam Phan (Paramignya trimera) has long been used in Viet Nam as an herbal medicine for the treatment of Hepatitis, hepatocellular carcinoma, and diabetes. This study aimed to determine the anti-proliferation effect of Paramignya trimera extract (P. trimera extract) on HepG2 hepatocellular carcinoma cells. Methods: AlamarBlue assay was used to determine the IC50 values of P. trimera extract on HepG2 cells. Adipose-derived stem cells (ADSCs) was used as normal cell control. For apoptosis examination, P. trimera extract-treated HepG2 cells were incubated with Annexin V/Propidium iodide (PI). Then they have been analyzed their expression of Annexin-V and PI by flow cytometry. The cell nuclear degradation also was evaluated by PI/Hoechst 33342 staining assay. Results: Doxorubicin and P. trimera extract IC50 values on HepG2 cells were 55.13 +/- 2.028 ng/ml and 582.533 +/- 16.521 mg/ml, respectively. Those on ADSCs were 5.96 +/- 0.56 ng/ml and 268.976 +/- 19.325 mg/ml, respectively. Side effect index value (SEI) of P. trimera extract was 2.175 +/- 0.12, and the SEI of doxorubicin was 8.71 +/- 0.36. Flow cytometry analysis indicated significant apoptosis on P. trimera extract-treated HepG2 cells at a dose of 500 mg/ml (32.39 +/- 2.28% apoptotic cells, and 14.63 +/- 1.59% necrotic cells). Nuclear aggregation and degradation was seen on 500 mg/ml P. trimera treated HepG2 cells. Conclusion: P. trimera extract could inhibit HepG2 hepatocellular carcinoma cell proliferation by inducing apoptosis.

N6-methyladenosine of chromosome-associated regulatory RNA regulates chromatin state and transcription

N6-methyladenosine (m6A) regulates stability and translation of messenger RNA (mRNA) in various biological processes. In this work, we show that knockout of the m6A writer Mettl3 or the nuclear reader Ythdc1 in mouse embryonic stem cells increases chromatin accessibility and activates transcription in an m6A-dependent manner. We found that METTL3 deposits m6A modifications on chromosome-associated regulatory RNAs (carRNAs), including promoter-associated RNAs, enhancer RNAs, and repeat RNAs. YTHDC1 facilitates the decay of a subset of these m6A-modified RNAs, especially elements of the long interspersed element-1 family, through the nuclear exosome targeting–mediated nuclear degradation. Reducing m6A methylation by METTL3 depletion or site-specific m6A demethylation of selected carRNAs elevates the levels of carRNAs and promotes open chromatin state and downstream transcription. Collectively, our results reveal that m6A on carRNAs can globally tune chromatin state and transcription.