Nucleobase self-assembly: aggregation, morphological characterization, and toxicity analysis

This study expands the platform for amyloidogenic building blocks, such as nucleobases, and their self-assembly. Here, we examine the self-assembly profile of nucleobases such as guanine, cytosine, and thymine and determine that these nucleobases, while aged, produce small globules which gradually transform into fibrillar assemblies. Notably, the amyloid-like fibrillation in adenine and uracil has already been reported; hence, it was imperative to understand the amyloidogenic propensity in these unexplored nucleobases. The aggregates formed by guanine, cytosine, and thymine interestingly reveal a distinctive spectrum characteristic of amyloidogenic proteins after binding to the amyloid-specific dye Thioflavin T (ThT). The MTT assay in human retinal pigment epithelial RPE-1 cell lines revealed the aggregates formed by these nucleobases are toxic with significantly more toxicity observed for aged samples as compared to the fresh ones. The in vivo assays in C. elegans nematodes further validated the toxicities induced by the aggregates and the heat shock survival assay suggests these metabolite assemblies affect the protein clearance machinery like other amyloids. Overall, the research offers additional support for the role of amyloidogenesis in IEMs and suggests a recognized toxicity mechanism for IEMs caused by the accumulation of nucleobases.