On Ternary FF-manifold Algebras and their Representations

We introduce a notion of ternary $F$-manifold algebras which is a generalization of $F$-manifold algebras. We study representation theory of ternary $F$-manifold algebras. In particular, we introduce a notion of dual representation which requires additional conditions similar to the binary case. We then establish a notion of a coherence ternary $F$-manifold algebra. Moreover, we investigate the construction of ternary $F$-manifold algebras using $F$-manifold algebras. Furthermore, we introduce and investigate a notion of a relative Rota-Baxter operator with respect to a representation and use it to construct ternary pre-$F$-manifold algebras.Comment: Comments are welcome. arXiv admin note: text overlap with arXiv:2102.05595; text overlap with arXiv:2002.10238 by other author

MRE11 Function in Response to Topoisomerase Poisons Is Independent of its Function in Double-Strand Break Repair in Saccharomyces cerevisiae

Camptothecin (CPT) and etoposide (ETP) trap topoisomerase-DNA covalent intermediates, resulting in formation of DNA damage that can be cytotoxic if unrepaired. CPT and ETP are prototypes for molecules widely used in chemotherapy of cancer, so defining the mechanisms for repair of damage induced by treatment with these compounds is of great interest. In S. cerevisiae, deficiency in MRE11, which encodes a highly conserved factor, greatly enhances sensitivity to treatment with CPT or ETP. This has been thought to reflect the importance of double-strand break (DSB) repair pathways in the response to these to agents. Here we report that an S. cerevisiae strain expressing the mre11-H59A allele, mutant at a conserved active site histidine, is sensitive to hydroxyurea and also to ionizing radiation, which induces DSBs, but not to CPT or ETP. We show that TDP1, which encodes a tyrosyl-DNA phosphodiesterase activity able to release both 5′- and 3′-covalent topoisomerase-DNA complexes in vitro, contributes to ETP-resistance but not CPT-resistance in the mre11-H59A background. We further show that CPT- and ETP-resistance mediated by MRE11 is independent of SAE2, and thus independent of the coordinated functions of MRE11 and SAE2 in homology-directed repair and removal of Spo11 from DNA ends in meiosis. These results identify a function for MRE11 in the response to topoisomerase poisons that is distinct from its functions in DSB repair or meiotic DNA processing. They also establish that cellular proficiency in repair of DSBs may not correlate with resistance to topoisomerase poisons, a finding with potential implications for stratification of tumors with specific DNA repair deficiencies for treatment with these compounds

SUMO modification of the neuroprotective protein TDP1 facilitates chromosomal single-strand break repair

Breaking and sealing one strand of DNA is an inherent feature of chromosome metabolism to overcome torsional barriers. Failure to reseal broken DNA strands results in protein-linked DNA breaks, causing neurodegeneration in humans. This is typified by defects in tyrosyl DNA phosphodiesterase 1 (TDP1), which removes stalled topoisomerase 1 peptides from DNA termini. Here we show that TDP1 is a substrate for modification by the small ubiquitin-like modifier SUMO. We purify SUMOylated TDP1 from mammalian cells and identify the SUMOylation site as lysine 111. While SUMOylation exhibits no impact on TDP1 catalytic activity, it promotes its accumulation at sites of DNA damage. A TDP1 SUMOylation-deficient mutant displays a reduced rate of repair of chromosomal single-strand breaks arising from transcription-associated topoisomerase 1 activity or oxidative stress. These data identify a role for SUMO during single-strand break repair, and suggest a mechanism for protecting the nervous system from genotoxic stress

SUMO-Targeted Ubiquitin Ligase, Rad60, and Nse2 SUMO Ligase Suppress Spontaneous Top1–Mediated DNA Damage and Genome Instability

Through as yet undefined proteins and pathways, the SUMO-targeted ubiquitin ligase (STUbL) suppresses genomic instability by ubiquitinating SUMO conjugated proteins and driving their proteasomal destruction. Here, we identify a critical function for fission yeast STUbL in suppressing spontaneous and chemically induced topoisomerase I (Top1)–mediated DNA damage. Strikingly, cells with reduced STUbL activity are dependent on tyrosyl–DNA phosphodiesterase 1 (Tdp1). This is notable, as cells lacking Tdp1 are largely aphenotypic in the vegetative cell cycle due to the existence of alternative pathways for the removal of covalent Top1–DNA adducts (Top1cc). We further identify Rad60, a SUMO mimetic and STUbL-interacting protein, and the SUMO E3 ligase Nse2 as critical Top1cc repair factors in cells lacking Tdp1. Detection of Top1ccs using chromatin immunoprecipitation and quantitative PCR shows that they are elevated in cells lacking Tdp1 and STUbL, Rad60, or Nse2 SUMO ligase activity. These unrepaired Top1ccs are shown to cause DNA damage, hyper-recombination, and checkpoint-mediated cell cycle arrest. We further determine that Tdp1 and the nucleotide excision repair endonuclease Rad16-Swi10 initiate the major Top1cc repair pathways of fission yeast. Tdp1-based repair is the predominant activity outside S phase, likely acting on transcription-coupled Top1cc. Epistasis analyses suggest that STUbL, Rad60, and Nse2 facilitate the Rad16-Swi10 pathway, parallel to Tdp1. Collectively, these results reveal a unified role for STUbL, Rad60, and Nse2 in protecting genome stability against spontaneous Top1-mediated DNA damage

Culex pipiens, an Experimental Efficient Vector of West Nile and Rift Valley Fever Viruses in the Maghreb Region

West Nile fever (WNF) and Rift Valley fever (RVF) are emerging diseases causing epidemics outside their natural range of distribution. West Nile virus (WNV) circulates widely and harmlessly in the old world among birds as amplifying hosts, and horses and humans as accidental dead-end hosts. Rift Valley fever virus (RVFV) re-emerges periodically in Africa causing massive outbreaks. In the Maghreb, eco-climatic and entomologic conditions are favourable for WNV and RVFV emergence. Both viruses are transmitted by mosquitoes belonging to the Culex pipiens complex. We evaluated the ability of different populations of Cx. pipiens from North Africa to transmit WNV and the avirulent RVFV Clone 13 strain. Mosquitoes collected in Algeria, Morocco, and Tunisia during the summer 2010 were experimentally infected with WNV and RVFV Clone 13 strain at titers of 107.8 and 108.5 plaque forming units/mL, respectively. Disseminated infection and transmission rates were estimated 14–21 days following the exposure to the infectious blood-meal. We show that 14 days after exposure to WNV, all mosquito st developed a high disseminated infection and were able to excrete infectious saliva. However, only 69.2% of mosquito strains developed a disseminated infection with RVFV Clone 13 strain, and among them, 77.8% were able to deliver virus through saliva. Thus, Cx. pipiens from the Maghreb are efficient experimental vectors to transmit WNV and to a lesser extent, RVFV Clone 13 strain. The epidemiologic importance of our findings should be considered in the light of other parameters related to mosquito ecology and biology

Assemblages of fungi associated with cork oak forests in northwestern Tunisia

The cork oak forests of Aïn Draham in northwestern Tunisia are characterized by a rich biodiversity of fungi, including edible, non-edible and toxic species. Sporocarps of 117 species of macrofungi collected from the forests of Jbel el Bir at different elevations were found to represent 26 families of the Agaricomycotina. Selected taxa are described herein, along with information on edibility and ecological importance. Among these there were 33 species of ectomycorrhizal fungi, 10 species of saprotrophic fungi and one species that is parasitic. Molecular identification of fungi from cork oak root-tips revealed the presence of such ectomycorrhizal species as Amanita rubescens, Laccaria bicolor, Lactarius subumbonatus, Cortinarius incisus, and Xerocomus rubellus along with a taxon identified only to genus level as Clavulina sp. Other taxa recorded from the rhizosphere of cork oak included Mortierellales and other mitosporic fungi (e. g., Sarcopodium circinatum)

Détection de la circulation de virus West Nile chez les Équidés dans le nord-ouest de la Tunisie

International audienceTwo outbreaks of West Nile Fever (FWN) were observed in the Sahel of Tunisia in 1997 and 2003. Several cases of meningitis and meningoencephalitis have been described in humans during these two outbreaks. However, no animal or clinical findings or seroconversion have been detected despite a high seroprevalence in human beings found around the affected areas. Few data are available regarding the spreading of this virus in other parts of the country. The purpose of this study was to detect a possible WNV spread in horses in some areas of Tunisia considered to be at risk for WNV but which had not been affected by previous outbreaks. A total of 133 equine blood samples were collected in six delegations from three governorates in the north-west of Tunisia. A second blood sampling was taken from animals that were tested negative after the first sampling for IgG to identify possible seroconversion. Detection of IgG was done using competitive ELISA. A significant viral spread was detected in the study area. Out of 133 samples tested for IgG during the first sampling, 36 samples were tested positive (27.1%). Two seroconversions were detected between September and October 2008 out of 84 samples tested. Statistical analysis showed a significant association between the presence of a wetland within 10 km and seroconversion. The presence of cattle seems to be a protective factor.Deux épidémies à virus West Nile (VWN) ont été observées dans la région du Sahel tunisien en 1997 et en 2003. Plusieurs cas de méningites et de méningoencéphalites ont été décrits chez l’Homme durant ces deux épidémies. Mais, aucun cas animal, ni clinique ni de séroconversion, n’a été rapporté. De plus, peu de données sont disponibles quant à la circulation de ce virus dans les autres régions du pays. Le but de la présente étude était de détecter une éventuelle circulation virale de VWN chez les Équidés dans certaines régions de la Tunisie où des épidémies n’ont pas été enregistrées auparavant. Un total de 133 Équidés a été prélevé dans six délégations appartenant à trois gouvernorats du nord-ouest de la Tunisie entre août et octobre 2008. Les Équidés qui se sont avérés négatifs en IgG au premier prélèvement ont fait l’objet d’un deuxième prélèvement ultérieur pour identifier de possibles séroconversions. L’analyse des IgG a été réalisée par Elisa compétitif. L’étude a permis de détecter une circulation virale dans la zone étudiée. Sur les 133 prélèvements testés en IgG lors de la première visite, 36 prélèvements étaient positifs ; soit une séroprévalence de l’ordre de 27,1 %. Une deuxième série de prélèvements a été réalisée sur 84 Équidés: le résultat s’était avéré négatif. Deux séroconversions ont été détectées entre les mois de septembre et d’octobre 2008. L’analyse a montré une association statistiquement significative entre la présence d’une zone humide à moins de 10 km et la séroprévalence. La présence de bovins semble être un facteur protecteur