Deoxynivalenol globally affects the selection of 3' splice sites in human cells by suppressing the splicing factors, U2AF1 and SF1

Fusariotoxin-Induced Toxicity in Mesenchymal Stem Cells and Fibroblasts: A Comparison Between Differentiated and Undifferentiated Cells

Objectives

Humans are unknowingly exposed to mycotoxins through the consumption of plant-derived foods and processed products contaminated with these toxic compounds. In addition to agricultural losses, Fusarium toxins pose a threat to human health. However, the effects of fusariotoxins on the viability and proliferation of stem cells have not been fully explored. We investigated the cytotoxic effects of deoxynivalenol (DON) and B-trichothecene mix (MIX) on mesenchymal stem cells (MSCs) and the L929 fibroblast cell line.

Materials and Methods

MSCs were isolated from the dental pulp tissue. The doubling time and viability of dental pulp stem cells (DPSCs) and L929 cells were determined using the MTT assay. The following doses of B-trichothecenes (0.25-16 µg/mL; 24 hours and 48 hours) were used to evaluate cytotoxicity. In addition, changes in the confluency-dependent response of DPSCs to DON toxicity were determined. Moreover, we investigated the effect of DON on cell death via acridine orange/ethidium bromide (AO/EB) double staining.

Results

A DON and MIX showed a dose- and time-dependent inhibitory effect on the proliferation of both cells. DPSCs exposed to DON for 48 hours (IC50 = 0.5 μg/mL) were found to be 16-fold more sensitive than L929 cells (IC50 = 8 μg/mL). Compared with a culture with 80% confluency, DPSCs from a 50% confluent culture were more sensitive to varying doses of DON (0.25-4 µg/mL, 24-48 hours). Moreover, AO/EB staining showed that treatment of DPSCs with DON led to a significant increase in cell death (17% for 2.4 µg/mL; 50% for 4.8 µg/mL).

Conclusion

This study reveals that undifferentiated MSCs are significantly more sensitive to DON than differentiated somatic cells (L929). Given that humans are frequently exposed to these mycotoxins, our findings imply that prolonged exposure to them may also have harmful effects on cellular differentiation and embryonic development.

Toxic mechanisms of the trichothecenes T-2 toxin and deoxynivalenol on protein synthesis

The toxic mechanisms of trichothecenes, including T-2 toxin and deoxynivalenol (DON), are closely related with their effects on protein synthesis. Increasing lines of evidence show that T-2 toxin can reduce the levels of tight junction proteins, and nuclear factor erythroid 2-related factor 2 (Nrf2) by disrupting cellular barriers and the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) and Nrf2/heme oxygenase (HO)-1 pathways. Moreover, it can inhibit aggrecan synthesis, thus causing Kashin-Beck disease. Regarding type B trichothecene, DON inhibits activation marker and β-catenin synthesis by acting on immune cells and the wingless/integrated (Wnt) pathway; it also inhibits cell proliferation and immune surveillance. In addition, DON has been shown to destroy tight junctions, glucose transport, and tumor endothelial marker 8, thus disturbing intestinal function and changing cell migration. This review summarizes the inhibitory effects of the trichothecenes T-2 toxin and DON on different protein synthesis, while discussing their underlying mechanisms. Focus is given to the effects of these toxins on tight junctions, aggrecan, activation markers, and hormones including testosterone under the influence of steroidogenic enzymes. This review can extend the current understanding of the effects of trichothecenes on protein synthesis and help to further understand their toxic mechanisms.

Systematic characterization of the branch point binding protein, splicing factor 1, gene family in plant development and stress responses

BACKGROUND

Among eukaryotic organisms, alternative splicing is an important process that can generate multiple transcripts from one same precursor messenger RNA, which greatly increase transcriptome and proteome diversity. This process is carried out by a super-protein complex defined as the spliceosome. Specifically, splicing factor 1/branchpoint binding protein (SF1/BBP) is a single protein that can bind to the intronic branchpoint sequence (BPS), connecting the 5' and 3' splice site binding complexes during early spliceosome assembly. The molecular function of this protein has been extensively investigated in yeast, metazoa and mammals. However, its counterpart in plants has been seldomly reported.

RESULTS

To this end, we conducted a systematic characterization of the SF1 gene family across plant lineages. In this work, a total of 92 sequences from 59 plant species were identified. Phylogenetic relationships of these sequences were constructed, and subsequent bioinformatic analysis suggested that this family likely originated from an ancient gene transposition duplication event. Most plant species were shown to maintain a single copy of this gene. Furthermore, an additional RNA binding motif (RRM) existed in most members of this gene family in comparison to their animal and yeast counterparts, indicating that their potential role was preserved in the plant lineage.

CONCLUSION

Our analysis presents general features of the gene and protein structure of this splicing factor family and will provide fundamental information for further functional studies in plants.