ABSTRACT
Accumulation of cytoplasmic inclusions containing fused in sarcoma (FUS), an RNA/DNA-binding protein, is a common hallmark of frontotemporal lobar degeneration and amyotrophic lateral sclerosis neuropathology. We have previously shown that DNA damage can trigger the cytoplasmic accumulation of N-terminally phosphorylated FUS. However, the functional consequences of N-terminal FUS phosphorylation are unknown. To gain insight into this question, we utilized proximity-dependent biotin labeling via ascorbate peroxidase 2 aired with mass spectrometry to investigate whether N-terminal phosphorylation alters the FUS protein-protein interaction network (interactome), and subsequently, FUS function. We report the first analysis comparing the interactomes of three FUS variants: homeostatic wildtype FUS (FUS WT), phosphomimetic FUS (FUS PM; a proxy for N-terminally phosphorylated FUS), and the toxic FUS proline 525 to leucine mutant (FUS P525L) that causes juvenile amyotrophic lateral sclerosis. We found that the phosphomimetic FUS interactome is uniquely enriched for a group of cytoplasmic proteins that mediate mRNA metabolism and translation, as well as nuclear proteins involved in the spliceosome and DNA repair functions. Furthermore, we identified and validated the RNA-induced silencing complex RNA helicase MOV10 as a novel interacting partner of FUS. Finally, we provide functional evidence that N-terminally phosphorylated FUS may disrupt homeostatic translation and steady-state levels of specific mRNA transcripts. Taken together, these results highlight phosphorylation as a unique modulator of the interactome and function of FUS.
Subject(s)
Amyotrophic Lateral Sclerosis , DNA Damage , RNA-Binding Protein FUS , Amyotrophic Lateral Sclerosis/metabolism , Humans , Mutation , Phosphorylation , RNA Helicases/metabolism , RNA, Messenger/metabolism , RNA-Binding Protein FUS/genetics , RNA-Binding Protein FUS/metabolism , RNA-Binding Proteins/metabolismABSTRACT
BACKGROUND: Gummy stem blight (GSB) is a devastating disease of cucurbits that has been effectively managed with fungicide applications. However, the Stagonosporopsis spp. that cause GSB have rapidly evolved resistance to multiple classes of fungicides. To better understand the evolution and persistence of fungicide resistance in field populations, resistance profiles of unique and clonal genotypes of 113 Stagonosporopsis citrulli and 19 S. caricae isolates to four different fungicides were determined based on in vitro mycelial growth assays and molecular markers based on genes encoding fungicide targets. RESULTS: All 19 S. caricae isolates screened were resistant to tebuconazole and azoxystrobin, and sensitive to boscalid and fluopyram. All 113 S. citrulli isolates were sensitive to tebuconazole and sensitive to fluopyram, with one exception that was fluopyram-resistant. All isolates of S. citrulli except two were resistant to azoxystrobin. Phenotypic differences in response to boscalid were detected among S. citrulli isolates, but the phenotypes were not associated with multilocus genotypes (MLG) determined by 16 microsatellite loci. Additionally, isolates sharing the same MLG varied by SdhB genotype. A unique mutation of I229V in SdhB, a target of succinate dehydrogenase inhibitor fungicides, was detected for the fluopyram-resistant isolate of S. citrulli. CONCLUSION: Both the lack of association of fungicide resistance profiles with genetic similarity of isolates based on microsatellite loci and the finding that widely distributed MLG varied in fungicide resistance profiles suggest that independent evolutionary events for resistance to boscalid have likely occurred. Frequent genetic recombination within populations may be responsible for resistance to multiple fungicides. This study provides useful information for effectively managing both species of GSB fungi present in the southeastern USA and understanding the evolution of fungicide resistance within populations of plant-pathogenic fungi. © 2019 Society of Chemical Industry.
