Dual computational and biological assessment of some promising nucleoside analogs against the COVID-19-Omicron variant.

Nucleoside analogs/derivatives (NAs/NDs) with potent antiviral activities are now deemed very convenient choices for the treatment of coronavirus disease 2019 (COVID-19) arisen by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. At the same time, the appearance of a new strain of SARS-CoV-2, the Omicron variant, necessitates multiplied efforts in fighting COVID-19. Counteracting the crucial SARS-CoV-2 enzymes RNA-dependent RNA polymerase (RdRp) and 3'-to-5' exoribonuclease (ExoN) jointly altogether using the same inhibitor is a quite successful new plan to demultiplicate SARS-CoV-2 particles and eliminate COVID-19 whatever the SARS-CoV-2 subtype is (due to the significant conservation nature of RdRps and ExoNs in the different SARS-CoV-2 strains). Successive in silico screening of known NAs finally disclosed six different promising NAs, which are riboprine/forodesine/tecadenoson/nelarabine/vidarabine/maribavir, respectively, that predictably can act through the planned dual-action mode. Further in vitro evaluations affirmed the anti-SARS-CoV-2/anti-COVID-19 potentials of these NAs, with riboprine and forodesine being at the top. The two NAs are able to effectively antagonize the replication of the new virulent SARS-CoV-2 strains with considerably minute in vitro anti-RdRp and anti-SARS-CoV-2 EC50 values of 189 and 408 nM for riboprine and 207 and 657 nM for forodesine, respectively, surpassing both remdesivir and the new anti-COVID-19 drug molnupiravir. Furthermore, the favorable structural characteristics of the two molecules qualify them for varied types of isosteric and analogistic chemical derivatization. In one word, the present important outcomes of this comprehensive dual study revealed the anticipating repurposing potentials of some known nucleosides, led by the two NAs riboprine and forodesine, to successfully discontinue the coronaviral-2 polymerase/exoribonuclease interactions with RNA nucleotides in the SARS-CoV-2 Omicron variant (BA.5 sublineage) and accordingly alleviate COVID-19 infections, motivating us to initiate the two drugs' diverse anti-COVID-19 pharmacological evaluations to add both of them betimes in the COVID-19 therapeutic protocols.

The coronavirus proofreading exoribonuclease mediates extensive viral recombination.

Recombination is proposed to be critical for coronavirus (CoV) diversity and emergence of SARS-CoV-2 and other zoonotic CoVs. While RNA recombination is required during normal CoV replication, the mechanisms and determinants of CoV recombination are not known. CoVs encode an RNA proofreading exoribonuclease (nsp14-ExoN) that is distinct from the CoV polymerase and is responsible for high-fidelity RNA synthesis, resistance to nucleoside analogues, immune evasion, and virulence. Here, we demonstrate that CoVs, including SARS-CoV-2, MERS-CoV, and the model CoV murine hepatitis virus (MHV), generate extensive and diverse recombination products during replication in culture. We show that the MHV nsp14-ExoN is required for native recombination, and that inactivation of ExoN results in decreased recombination frequency and altered recombination products. These results add yet another critical function to nsp14-ExoN, highlight the uniqueness of the evolved coronavirus replicase, and further emphasize nsp14-ExoN as a central, completely conserved, and vulnerable target for inhibitors and attenuation of SARS-CoV-2 and future emerging zoonotic CoVs.

Circular RNA hsa_circ_0007364 increases cervical cancer progression through activating methionine adenosyltransferase II alpha (MAT2A) expression by restraining microRNA-101-5p.

Emerging evidence suggested that circular RNAs (circRNAs) play critical roles in cervical cancer (CC) progression. However, the roles and molecular mechanisms of hsa_circ_0007364 in the tumorigenesis of CC remain unclear. In the present study, we used bioinformatics analysis and a series of experimental analysis to characterize a novel circRNA, hsa_circ_0007364 was up-regulated and associated with advanced clinical features in CC patients. Hsa_circ_0007364 inhibition notably suppressed the proliferation and invasion abilities of CC cells in vitro and reduced tumor growth in vivo. Moreover, hsa_circ_0007364 was uncovered to sponge miR-101-5p. Additionally, methionine adenosyltransferase II alpha (MAT2A) was verified as a target gene of miR-101-5p, and its downregulation reversed the inhibitory effects of hsa_circ_0007364 knockdown on CC progression. Therefore, we suggested that hsa_circ_0007364 might serve as an oncogenic circRNA in CC progression by regulating the miR-101-5p/MAT2A axis, which provides a potential therapeutic target to the treatment. Research highlights hsa_circ_0007364 was upregulated in CC hsa_circ_0007364 promoted CC cell progression hsa_circ_0007364/miR-101-5p/MAT2A axis in CC.

The interferon stimulated gene 20 protein (ISG20) is an innate defense antiviral factor that discriminates self versus non-self translation.

ISG20 is a broad spectrum antiviral protein thought to directly degrade viral RNA. However, this mechanism of inhibition remains controversial. Using the Vesicular Stomatitis Virus (VSV) as a model RNA virus, we show here that ISG20 interferes with viral replication by decreasing protein synthesis in the absence of RNA degradation. Importantly, we demonstrate that ISG20 exerts a translational control over a large panel of non-self RNA substrates including those originating from transfected DNA, while sparing endogenous transcripts. This activity correlates with the protein's ability to localize in cytoplasmic processing bodies. Finally, these functions are conserved in the ISG20 murine ortholog, whose genetic ablation results in mice with increased susceptibility to viral infection. Overall, our results posit ISG20 as an important defense factor able to discriminate the self/non-self origins of the RNA through translation modulation.

Identification of a new HLA-A*0201-restricted cytotoxic T lymphocyte epitope from CML28.

Identification of cytotoxic T lymphocyte (CTL) epitopes from additional tumor antigens is essential for the development of specific immunotherapy of malignant tumors. CML28, a recently discovered cancer-testis (CT) antigen from chronic myelogenous leukemia, is considered to be a promising target of tumor-specific immunotherapy. Because HLA-A*0201 is one of the most common histocompatibility molecule in Chinese, we aim at identifying CML28 peptides presented by HLA-A*0201. A panel of CML28-derived antigenic peptides was predicted using a computer-based program. Four peptides with highest predicted score were synthesized and tested for their binding affinities to HLA-A*0201 molecule. Then these peptides were assessed for their immunogenicity to elicit specific immune responses mediated by CTLs both in vitro, from PBMCs sourced from four healthy HLA-A*0201(+) donors, and in vivo, in HLA-A*0201 transgenic mice. One of the tested peptides, CML28((173-181)), induced peptide-specific CTLs in vitro as well as in vivo, which could specifically secrete IFN-gamma and lyse major histocompatibility complex (MHC)-matched tumor cell lines endogenously expressing CML28 antigen and CML28((173-181) )pulsed Jurkat-A2/Kb cells, respectively. These results demonstrate that CML28((173-181) )is a naturally processed and presented CTL epitope with HLA-A*0201 motif and has a promising immunogenicity both in vitro and in vivo. As CML28 is expressed in a large variety of histological tumors besides chronic myelogenous leukemia, we propose that the newly identified epitope, CML28((173-181)), would be of potential use in peptide-based, cancer-specific immunotherapy against a broad spectrum of tumors.

Characterization of polytropic MuLVs from three-week-old AKR/J mice.

An immunological focus assay using monoclonal antibodies on live adherent in vitro cell lines was employed to detect and isolate different types of murine leukemia viruses (MuLVs) from spleen and thymus cells of young (less than 1 month of age) AKR/J mice. In agreement with earlier studies, ecotropic viruses were detected from cells of both tissues in all mice tested, although only trace levels of ecotropic MuLV infectious centers were found with thymus cells from mice of this age. Polytropic MuLVs were not detected in mice less than 3 weeks of age; however, between the ages of 3 and 4 weeks, polytropic viruses were detectable in assays of spleen cells from 50% of the mice. No polytropic MuLVs were detected in assays of thymocytes from any mice of this age. Several polytropic MuLVs obtained from spleens of young mice were further characterized. All of the isolates were infectious for both mink and SC-1 (feral mouse) cells, and exhibited interference properties typical of polytropic MuLVs. However, none of the viruses induced obvious cytopathic effects (CPE) on mink cells. All of the viruses appeared antigenically similar with regard to their reactivities to a panel of 12 monoclonal antibodies directed at envelope antigens of polytropic MuLVs. RNase T1-resistant oligonucleotide analysis of a polytropic MuLV from a 26-day-old mouse indicated that its entire env gene was derived from nonecotropic sequences while the remainder of its genome was indistinguishable from the ecotropic parent. The isolate thus exhibited a genome structure typical of Class II polytropic MuLVs and is the first example of this type of MuLV isolated from AKR/J mice. Examination of polytropic MuLVs derived from the spleens and thymuses of 5- to 6-month-old mice indicated that only 2 of 10 isolates examined induced CPE on mink cells. Furthermore, most of the CPE-negative viruses isolated from spleen and thymus cells of these mice exhibited in vitro host ranges and antigenic reactivities similar to isolates from young mice, suggesting that this type of polytropic MuLV may originate in the spleen, subsequently spread to other tissues, and persist throughout the preleukemic period. The detection of polytropic viruses in a large proportion of very young mice is in contrast to previous studies which have not detected polytropic virus production in AKR mice less than 5 to 6 months of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Application of halophilic nuclease H of Micrococcus varians subsp. halophilus to commercial production of flavoring agent 5'-GMP.

RNA was degraded at 60 degrees C for 24 h by halophilic nuclease H in supernatants from broth cultures of Micrococcus varians subsp. halophilus containing 12% NaCl. Since contaminating 5'-nucleotidase exhibited almost no activity under these conditions, the 5'-GMP formed could be recovered from the reaction mixture, and the yield was 805 mg from 5 g of RNA.