Therapeutic promise of engineered nonsense suppressor tRNAs

Abstract

Nonsense mutations change an amino acid codon to a premature termination codon (PTC) generally through a single‐nucleotide substitution. The generation of a PTC results in a defective truncated protein and often in severe forms of disease. Because of the exceedingly high prevalence of nonsense‐associated diseases and a unifying mechanism, there has been a concerted effort to identify PTC therapeutics. Most clinical trials for PTC therapeutics have been conducted with small molecules that promote PTC read through and incorporation of a near‐cognate amino acid. However, there is a need for PTC suppression agents that recode PTCs with the correct amino acid while being applicable to PTC mutations in many different genomic landscapes. With these characteristics, a single therapeutic will be able to treat several disease‐causing PTCs. In this review, we will focus on the use of nonsense suppression technologies, in particular, suppressor tRNAs (sup‐tRNAs), as possible therapeutics for correcting PTCs. Sup‐tRNAs have many attractive qualities as possible therapeutic agents although there are knowledge gaps on their function in mammalian cells and technical hurdles that need to be overcome before their promise is realized. This article is categorized under: RNA Processing > tRNA Processing Translation > Translation Regulation

Efficient Suppression of Endogenous CFTR Nonsense Mutations Using Anticodon Engineered Transfer RNAs

“…While results shown by ourselves and others indicate the safety of ACE-tRNAs, the DNA delivery methods used here require the use of a transfection marker to control for efficient DNA delivery and cannot be directly translated to the clinic. This highlights a remaining roadblock of delivery to the clinical implementation of ACE-tRNAs, however it should be noted that tRNAs as gene therapy cargo possess a number of attractive qualities (31). We have shown here that ACE-tRNAs can be delivered as RNA or DNA, for which there are many therapeutically relevant delivery avenues to pursue.…”

“…Another nonsense suppression technology that has been explored previously is the use of nonsense suppressor tRNAs or anticodon edited tRNAs (ACE-tRNAs) (5,(27)(28)(29)(30)(31). A recently developed library of ACE-tRNAs with the anticodons engineered via mutagenesis to suppress one of the UAA, UAG, or UGA PTC codons demonstrated efficacious in vivo PTC suppression (30).…”

Repurposing tRNAs for nonsense suppression

“…Historically, the use of repurposed tRNAs to decode stop codons has been an attractive strategy proposed already to correct nonsense mutations causally linked to various diseases (reviewed in ref. 8 ). Despite its enormous therapeutic potential, up to date no clinical trial has been launched.…”

“…Nonsense mutations within protein-coding sequences convert a sense triplet into a stop codon, which in humans is connected to various devastating pathologies 7,8 . In a few species, the detrimental effects of pervasive nonsense mutations are kept low by suppressor tRNAs, which commonly arise by mutation in a tRNA's anticodon 9 to decode the newly arising stop codon.…”

Therapeutic Approaches for Patients with Cystic Fibrosis Not Eligible for Current CFTR Modulators

“…Anticodon-engineered suppressor tRNAs (ACE tRNAs) may be beneficial for patients with cystic fibrosis bearing nonsense mutations. They are designed to carry a nonsensesuppressing anticodon to address PTCs and to introduce the correct amino acid in the elongating peptide [25]. They are recognized by the endogenous translation cellular machinery, including the aminoacyl-tRNA synthetase that charges the ACE-tRNA with their cognate amino acid and the eukaryotic elongation factor 1α (eEF-1α), which delivers the charged tRNA to the ribosome.…”