Function and clinical significance of N6-methyladenosine in digestive system tumours

RNA modification, like DNA methylation, histone modification, non-coding RNA modification and chromatin rearrangement, plays an important role in tumours. N6-methyladenosine (m6A) is the most abundant RNA modification in cells, and it regulates RNA transcription, processing, splicing, degradation, and translation. m6A-associated proteins have been used as new biomarkers and therapeutic targets for tumour prediction and monitoring. There are three main types of proteins involved in m6A methylation: methyltransferases (METTL3, METTL14, WTAP, RBM15, ZC3H13 and KIAA1429), demethylases (FTO, ALKBH5 and ALKBH3) and RNA-binding proteins (YTHDF1-3, YTHDC1-2, IGF2BPs and HNRNPs). This article reviews the origins, characteristics and functions of m6A and its relationship with digestive system tumours based on recent research. The expression of m6A regulators can be used as an evaluation indicator of tumour growth and progression and as a prognostic indicator. In-depth research on m6A methylation in digestive system tumours may provide new directions for clinical prediction and further treatment.

An in silico LLPS perturbation approach in the design of a novel SARS-CoV-2 spike receptor-binding domain inhibitor

The reversible process where a homogenous fluid de-mixes into two distinctively separate liquid phases is referred to as LLPS (Liquid-liquid phase separation). The resulting liquid is made up of one dilute phase and one condensed phase. An increasing number of studies have shown that the liquid-liquid phase separation is an important principle that underlies intracellular organization in biological systems, forming liquid condensates without a membrane envelope, otherwise known as MLOs (membraneless organelles). Such organelles include the P bodies, nucleolus and stress granules. Moreover, the regulation of many other biological processes such as signal transduction, chromatin rearrangement and RNA metabolism have been linked to the liquid-liquid phase separation.

TRF1 averts chromatin remodelling, recombination and replication dependent-break induced replication at mouse telomeres

Telomeres are a significant challenge to DNA replication and are prone to replication stress and telomere fragility. The shelterin component TRF1 facilitates telomere replication but the molecular mechanism remains uncertain. By interrogating the proteomic composition of telomeres, we show that mouse telomeres lacking TRF1 undergo protein composition reorganisation associated with the recruitment of DNA damage response and chromatin remodellers. Surprisingly, mTRF1 suppresses the accumulation of promyelocytic leukemia (PML) protein, BRCA1 and the SMC5/6 complex at telomeres, which is associated with increased Homologous Recombination (HR) and TERRA transcription. We uncovered a previously unappreciated role for mTRF1 in the suppression of telomere recombination, dependent on SMC5 and also POLD3 dependent Break Induced Replication at telomeres. We propose that TRF1 facilitates S-phase telomeric DNA synthesis to prevent illegitimate mitotic DNA recombination and chromatin rearrangement.

TRF1 prevents permissive DNA damage response, recombination and Break Induced Replication at telomeres

Telomeres are a significant challenge to DNA replication and are prone to replication stress and telomere fragility. The shelterin component TRF1 facilitates telomere replication but the molecular mechanism remains uncertain. By interrogating the proteomic composition of telomeres, we show that telomeres lacking TRF1 undergo protein composition reorganisation associated with a DNA damage response and chromatin remodelers. Surprisingly, TRF1 suppresses the accumulation of promyelocytic leukemia (PML) protein, BRCA1 and the SMC5/6 complex at telomeres, which is associated with increased Homologous Recombination (HR) and TERRA transcription. We uncovered a previously unappreciated role for TRF1 in the suppression of telomere recombination, dependent on SMC5 and also POLD3 dependent Break Induced Replication at telomeres. We propose that TRF1 facilitates S-phase telomeric DNA synthesis to prevent illegitimate mitotic DNA recombination and chromatin rearrangement.

Novel Acaricidal Drug Fluazuron Causes Immunotoxicity via Selective Depletion of Lymphocytes T CD8

Fluazuron is one of the newest veterinary antitick medicines. Belonging to the benzoylphenylureas group, its mechanism of action acts by the interference of the formation of the chitin of the tick, which is responsible for the hardening of its exoskeletons. In addition to taking care of the health of the animal so that it receives the medication in the doses and the correct form, it is important to analyze the safety of the operator. Reduced resistance to infectious disease was a well-documented consequence of primary and acquired immunodeficiencies, but a novel finding following xenobiotic exposure. The awareness of the consequences of altered immune function is the most likely outcome of inadvertent exposure. The human health implications of studies in which chemical exposure reduced resistance to infection drove an early focus on immunosuppression within the toxicology community. The main objective is to perform the evaluation by computational platforms and in cell culture, searching for data that can serve as a foundation for a better understanding of the toxic effects involved with the accidental contamination of Fluazuron and, thus, to assist the medical community and users to understand the risks inherent in its use. As far as we can determine in the literature, our work has unmistakably demonstrated that the Fluazuron can cause genotoxicity by probable chromatin rearrangement and immunodepleting by specific reduction of the CD8 T lymphocyte subpopulation, mediated by the decrease in gamma interferon production. Although the use of Fluazuron is a necessity for tick control and for cattle management, we must bear in mind that the imminent risks to its application exist. Careless use can damage the immune system which in turn carries a gigantic hazard by opening a door to diseases and pathogens and leaving us defenseless.

NF-Y controls fidelity of transcription initiation at gene promoters through maintenance of the nucleosome-depleted region

ABSTRACTFaithful transcription initiation is critical for accurate gene expression, yet the mechanisms underlying specific transcription start site (TSS) selection in mammals remain unclear. Here, we show that the histone-fold domain protein NF-Y, a ubiquitously expressed transcription factor, controls the fidelity of transcription initiation at gene promoters. We report that NF-Y maintains the region upstream of TSSs in a nucleosome-depleted state while simultaneously protecting this accessible region against aberrant and/or ectopic transcription initiation. We find that loss of NF-Y binding in mammalian cells disrupts the promoter chromatin landscape, leading to nucleosomal encroachment over the canonical TSS. Importantly, this chromatin rearrangement is accompanied by upstream relocation of the transcription preinitiation complex and ectopic transcription initiation. Further, this phenomenon generates aberrant extended transcripts that undergo translation, disrupting gene expression profiles. These results establish NF-Y as a central player in TSS selection in metazoans and highlight the deleterious consequences of inaccurate transcription initiation.

Microsurgical nuclear transfer by intraooplasmic karyoplast injection as an alternative embryo reconstruction method in somatic cloning of pigs and other mammal species; application value of the method and its technical advantages: a review

The introduction of cell nuclei into enucleated recipient cells, beyond enucleation, is the most significant stage of somatic cloning procedure. Microsurgical transfer of somatic nuclei can be an alternative method of clonal nuclear-cytoplasmic hybrid reconstruction towards cell fusion induced in the electric field, not only from the aspect of molecular mechanisms of nuclear chromatin rearrangement, advantageously influencing epigenetic reprogramming and structural remodelling of exogenous genetic material but also because in recent studies on pig cloning it was proved that the effectiveness of piezo-driven microinjection of ear-derived fibroblast karyoplasts measured by the percentage of oocytes preserving vitality after the cell nuclei transplantation operation did not differ significantly from the survival rate (viability) of clonal cybrids reconstituted by an electrofusion method. An intraooplasmic injection system of karyoplasts prepared from cells at G0/G1 or G2/M stages of cell cycle could also increase considerably the total efficiency of somatic cloning technique in pigs and in other mammal species.  

Molecular conditions of the cell nucleus remodelling/reprogramming process and nuclear-transferred embryo development in the intraooplasmic karyoplast injection technique: a review

The introduction of cell nuclei into enucleated recipient cells, beyond enucleation, is the most significant stage of somatic cloning procedure. Microsurgical transfer of somatic nuclei can be an alternative method of clonal nuclear-cytoplasmic hybrid reconstruction towards cell fusion induced in the electric field, not only from the aspect of molecular mechanisms of nuclear chromatin rearrangement, advantageously influencing epigenetic reprogramming and structural remodelling of exogenous genetic material, but also because it was proved in recent studies on pig cloning that the effectiveness of piezo-driven microinjection of ear-derived fibroblast karyoplasts measured by the percentage of oocytes preserving vitality after cell nuclei transplantation operation did not differ significantly from the survival rate (viability) of clonal cybrids reconstituted by an electrofusion method. The intraooplasmic injection system of karyoplasts prepared from cells at G0/G1 or G2/M stages of cell cycle could also increase considerably the total efficiency of somatic cloning technique in pigs and other mammal species.    

Directional mapping of DNA nicking in ejaculated and cauda epididymidal spermatozoa of the short-beaked echidna (Tachyglossus aculeatus: Monotremata)

Prototherian spermatozoa are unique amongst the Mammalia in terms of their filiform morphology, tandem arrangement of chromosomes and formation of sperm bundles. In the present study, we provide observations of echidna spermatozoa and note that the superstructure of the bundle is engineered around the shape of the individual sperm head and that this in turn may be a consequence of the unusual circumferential and helicoidal condensation of the DNA during spermiogenesis. Frozen–thawed ejaculated echidna spermatozoa were incubated and examined for the presence of non-typical DNA conformation by means of in situ labelling of DNA breaks using Klenow polymerase and via alkaline single-cell comet assays for detection of fragmented DNA. Both techniques successfully revealed the presence of what appeared to be directional DNA nicking, co-localised with the presence of highly sensitive alkali sites along the length of the sperm nucleus. It was not possible to define whether these alternative DNA configurations were associated with a failure of the sperm nucleus to condense appropriately during spermiogenesis or were evidence of DNA fragmentation following post-thaw incubation or a sequential structural chromatin rearrangement necessary for fertilisation.