Design, Synthesis, and Antifungal Activity of Novel Aryl-1,2,3-Triazole-ß-Carboline Hybrids.

The copper catalytic azide and terminal alkyne cycloaddition reaction, namely "click chemistry", gives a new and convenient way to create l,4-disubstitutd-l,2,3-triazoles. In this work, 2-pyrrolecarbaldiminato⁻Cu(II) complexes were established as efficient catalysts for the three-component 1,3-dipolar cycloaddition reaction of arylboronic acid and sodium azide (NaN3) with terminal alkynes in ethanol at room temperature to 50 °C, 1,4-disubstituted 1,2,3-triazoles were synthesized. Following the optimized protocol, two series of new aryl-1,2,3-triazole-ß-carboline hybrids have been designed and synthesized, and the chemical structures were characterized by ¹H NMR, 13C NMR, and high-resolution mass spectrometry (HRMS). All of the target compounds were evaluated in vitro for their antifungal activity against Rhizoctorzia solani, Fusarium oxysporum, Botrytis cinerea Pers., sunflower sclerotinia rot, and rape sclerotinia rot by mycelia growth inhibition assay at 50 µg/mL. The antifungal evaluation of the novel hybrids showed that, among the tested compounds, 5a, 5b, 5c, and 9b showed good antifungal activity against sunflower sclerotinia rot. Specifically, compound 9b also exhibited high broad-spectrum fungicidal against all the tested fungi with inhibition rates of 58.3%, 18.52%, 63.07%, 84.47%, and 81.23%. However, for F. oxysporum, all the target compounds showed no in vitro antifungal activities with an inhibition rate lower than 20%. These results provide an encouraging framework that could lead to the development of potent novel antifungal agents.

UBE4A catalyzes NRF1 ubiquitination and facilitates DDI2-mediated NRF1 cleavage.

The transcription factor nuclear factor erythroid 2 like 1 (NFE2L1 or NRF1) regulates constitutive and inducible expression of proteasome subunits and assembly chaperones. The precursor of NRF1 is integrated into the endoplasmic reticulum (ER) and can be retrotranslocated from the ER to the cytosol where it is processed by ubiquitin-directed endoprotease DDI2. DDI2 cleaves and activates NRF1 only when NRF1 is highly polyubiquitinated. It remains unclear how retrotranslocated NRF1 is primed with large amount of ubiquitin and/or very long polyubiquitin chain for subsequent processing. Here, we report that E3 ligase UBE4A catalyzes ubiquitination of retrotranslocated NRF1 and promotes its cleavage. Depletion of UBE4A reduces the amount of ubiquitin modified on NRF1, shortens the average length of polyubiquitin chain, decreases NRF1 cleavage efficiency and causes accumulation of non-cleaved, inactivated NRF1. Expression of a UBE4A mutant lacking ligase activity impairs the cleavage, likely due to a dominant negative effect. UBE4A interacts with NRF1 and the recombinant UBE4A can promote ubiquitination of retrotranslocated NRF1 in vitro. In addition, knocking out UBE4A reduces transcription of proteasomal subunits in cells. Our results indicate that UBE4A primes NRF1 for DDI2-mediated activation to facilitate expression of proteasomal genes.