Biology subjects

Ahern, C. A.

Publications and source records attributed to Ahern, C. A..

3 recordsLinked to original sources

bioRxiv2018

Engineered transfer RNAs for suppression of premature termination codons

Premature termination codons (PTCs) are responsible for 10-15% of all inherited disease. PTC suppression during translation offers a promising approach to treat a variety of genetic disorders, yet small molecules that promote PTC read-through have yielded mixed performance in clinical trials. We present a high-throughput, cell-based assay to identify anticodon engineered transfer RNAs (ACE-tRNA) which can effectively suppress in-frame PTCs and faithfully encode their cognate amino acid. In total, we identified ACE-tRNA with a high degree of suppression activity targeting the most common human disease-causing nonsense codons. Genome-wide transcriptome ribosome profiling of cells expressing ACE-tRNA at levels which repair PTC indicate that there are limited interactions with translation termination codons. These ACE-tRNAs display high suppression potency in mammalian cells, Xenopus oocytes and mice in vivo, producing PTC repair in multiple genes, including disease causing mutations within the cystic fibrosis transmembrane conductance regulator (CFTR).

molecular biology↗

bioRxiv2017

Conformational Dynamics In TRPV1 Channels Reported By An Encoded Coumarin Amino Acid

Transient Receptor Potential Vanilloid (TRPV1) channels support the detection and integration of nociceptive input. Currently available functional and structural data suggest that that TRPV1 channels have two potential gates within their cation selective permeation pathway: a barrier formed by a bundle crossing at the intracellular entrance and a second constriction created by the ion selectivity filter. To describe conformational changes associated with channel gating within the pore, the fluorescent non-canonical amino acid (f- ncAA) coumarin-tyrosine was genetically encoded at Y671, a residue proximal to the selectivity filter. TRPV1 channels expressing coumarin at either site displayed normal voltage- and agonist-dependent gating. Next, total internal reflection microscopy (TIRF) was performed to enable ultra-rapid, millisecond imaging of the conformational dynamics in single TRPV1 channels in live cells. Here, the data obtained from channels expressed in human derived cells show that optical fluctuations, photon counts, and variance of noise analysis from Y671 coumarin encoded in TRPV1 tetramers correlates closely with channel activation by capsaicin, thus providing an direct optical marker of channel activation at the selectivity filter. In companion molecular dynamics simulations, Y671 displays alternating solvent exposure between the closed and open states, giving support to the optical data. These calculations further suggest a direct involvement of Y671 in controlling the relative position of the pore helix and its role in supporting ionic conductance at the TRPV1 selectivity filter.

biophysics↗

bioRxiv2016

Engineered tRNA suppression of a CFTR nonsense mutation

Ten percent of human diseases are caused by nonsense mutations that lead to premature truncation of the protein reading frame. Small molecules that promote read-through of such PTC have significant clinical promise but current iterations suffer from low in vivo efficacy and the nonselective amino acid incorporation. Alternatively, while gene-modifying approaches, such as CRISPR/Cas9, represent a long-term solution, such treatments may be far from reaching the clinical setting. Building on previous work by our group and others, we describe a tRNA engineering approach that enables the conversion of an in frame nonsense stop mutation to the naturally occurring amino acid, thus rescuing the full-length wild type protein. Data is presented demonstrating the functionality of the approach with the rescue of CFTR W1282X, a human mutation that causes cystic fibrosis (CF). The stringency of the approach is confirmed by mass spectrometry in a model protein indicating the encoding of only tryptophan at the TGA suppression site. The data describe the first use of an edited tRNA to repair a CF causative mutation and serve a proof of principle for the eventual use of codon-edited tRNA for the therapeutic rescue of PTC disease codons.

cell biology↗