# Modulation of translation by synonomous codons in yeast

> **NIH NIH R01** · UNIVERSITY OF ROCHESTER · 2020 · $323,400

## Abstract

Project Summary
 Translation of the genetic code from mRNA into protein ultimately determines the protein composition of
the cell. Translation elongation and its fidelity are essential for human health, as mutations in translation factors
can result in intellectual disability. Translation elongation is modulated by the choice of synonymous codons
used to encode a polypeptide and is subject to multiple quality control mechanisms to prevent synthesis of
aberrant proteins. In the yeast Saccharomyces cerevisiae, translation of CGA-CGA codon pairs is strongly
inhibitory, much more so than any single codon. Inhibition is mediated by ribosomal protein Asc1 (human
RACK1), which triggers engagement of the ribosome quality control (RQC) system when ribosomes collide. To
define the scope and mechanisms of codon-mediated effects on translation, we recently used a high
throughput assay of GFP variants to identify 17 strongly inhibitory codon pairs, 12 of which are among the
most slowly translated codon pairs in yeast. We infer that these pairs are functionally important, as the most
slowly translated pairs are highly conserved in the corresponding positions of genes in closely related species.
 We are also studying the crucial process of reading frame maintenance, one of the most basic functions of
the ribosome. We had found that strains lacking Asc1 undergo extensive frameshifting at CGA codon repeats.
Using a genetic selection, we recently identified two additional proteins that work together with Asc1 to prevent
frameshifting at CGA repeats: uS3/Rps3, a universally conserved ribosomal protein, and Mbf1, an
archaeal/eukaryotic conserved protein, whose role in translation is poorly understood. Despite intensive study
of reading frame maintenance, this entire system involving Asc1, Mbf1, and Rps3, which is specific to
eukaryotes, has never been studied.
 Additional preliminary results have implicated two other proteins in reading frame maintenance: eS26 and
Gcn1. Ribosomal protein eS26 sits at the interface of collided ribosomes, which have recently been implicated
in frameshifting. Gcn1 is a major regulator of a conserved stress response pathway, involved in sensing
uncharged tRNA at the A-site of the ribosome when ribosomes are stalled due to amino acid starvation.
 Remarkably, three of the twelve most inhibitory codon pairs respond to the RQC system and require Mbf1
for reading frame maintenance, and nine other inhibitory codon pairs do not. The mechanisms by which these
nine pairs exert their effects on translation are a mystery, but seem likely to involve central components of the
translational control systems as many of these pairs are highly conserved and slowly translated.
 To follow up on these results we propose to 1. Determine the mechanisms by which Mbf1, Rps3 and Asc1
work to maintain the reading frame. 2. Investigate the roles of Rps26 and Gcn1 proteins in frameshifting. 3.
Define the mechanisms by which distinct inhibitory codon pairs exert the...

## Key facts

- **NIH application ID:** 10050347
- **Project number:** 2R01GM118386-05
- **Recipient organization:** UNIVERSITY OF ROCHESTER
- **Principal Investigator:** Elizabeth Joan Grayhack
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $323,400
- **Award type:** 2
- **Project period:** 2016-07-01 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10050347

## Citation

> US National Institutes of Health, RePORTER application 10050347, Modulation of translation by synonomous codons in yeast (2R01GM118386-05). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10050347. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*