Biology subjects

Waldron, J. A.

Publications and source records attributed to Waldron, J. A..

5 recordsLinked to original sources

bioRxiv2025

Codon-dependent regulation of mRNA translation and stability by ZC3H7A and ZC3H7B RNA-binding proteins

Decelerated translation elongation caused by non-optimal codons can reduce mRNA stability through codon optimality-mediated mRNA degradation. A key element of this process is the coupling of sensing the mRNA codon usage with the regulation of translation efficiency and stability. We report that two paralog RNA-binding proteins (ZC3H7A and ZC3H7B), which are only found in Chordates, preferentially bind to and reduce the stability and translation of mRNAs enriched in non-optimal codons with A/U at their wobble sites (A/U3 codons). ZC3H7A/B engage with ribosomes that lack elongation factors and induce mRNA degradation or block translation initiation through their interactions with the CCR4-NOT and the GIGYF2/4EHP translation repressor complex, respectively. Depletion of ZC3H7A/B or 4EHP impairs the repression of non-optimal A/U3-rich mRNAs. This study provides insights into a unique mechanism in higher eukaryotes that couples codon usage with the regulation of translation efficiency and mRNA stability.

cell biology↗

bioRxiv2025

The differential mechanisms of eIF4A1-mediated translational activation instructed by distinct RNA features

All mRNAs require eukaryotic translation initiation factor (eIF) 4A1 for translation through its different functions: loading of the pre-initiation complex onto mRNAs and unwinding of RNA structure. eIF4A1 is the catalytic subunit of the cap- binding eIF4F complex and presumed to select the mRNAs for translation through these activities, instructed by signalling pathways driving cell fate. The mechanisms underlying activation of the distinct eIF4A1 functions and establish translational selectivity are unknown. Here, we have unravelled the complexity of mRNA selection by eIF4A1. We have mechanistically characterised the biological and atomic basis of inhibition by gain- and loss-of-function eIF4A1-inhibitors eFT226 and hippuristanol, and used machine learning to model the mRNA features associated with specific inhibition. This uncovered the eIF4A1 function - mRNA sequence relationship: 5UTRs containing C/CG-rich require efficient mRNA loading by eIF4F which is specifically targeted by hippuristanol, while 5UTRs harbouring alternatives starts sites together with AG-rich motifs utilise eIF4A1 for start site selection, specifically perturbed by eFT226. Our model is validated through a massively parallel reporter assay using 5UTRs from a distinct evolutionary origin. This prompted us to examine the conservation between mRNA sequence and eIF4A1 function, and revealed their co- development. Our findings highlight opportunities for novel therapeutic strategies targeting eIF4A1 and for improved design of mRNA-based therapeutics.

cell biology↗

bioRxiv2023

eIF4A1 is essential for reprogramming the translational landscape of Wnt-driven colorectal cancers

Dysregulated translation is a hallmark of cancer. Targeting the translational machinery represents a therapeutic avenue which is being actively explored. eIF4A inhibitors target both eIF4A1, which promotes translation as part of the eIF4F complex, and eIF4A2, which can repress translation via the CCR4-NOT complex. While high eIF4A1 expression is associated with poor patient outcome, the role of eIF4A2 in cancer remains unclear. Furthermore, the on-target toxicity of targeting specific eIF4A paralogues in healthy tissue is under-explored. We show that while loss of either paralogue is tolerated in the wild-type intestine, eIF4A1 is specifically required to support the translational demands of oncogenic Wnt signalling. Intestinal tumourigenesis is suppressed in colorectal cancer models following loss of eIF4A1 but accelerated following loss of eIF4A2, while eIF4A inhibition with eFT226 mimics loss of eIF4A1 in these models.

cancer biology↗

bioRxiv2023

Optimisation of sample preparation from primary mouse tissue to maintain RNA integrity for methods examining translational control

Protein output of different mRNAs can vary by two orders of magnitude therefore it is critical to understand the processes that control gene expression that operate at the level of translation. Translatome-wide techniques such as polysome profiling and ribosome profiling are key methods for determining translations rates occurring on specific mRNAs. These techniques are now widely used in cell lines; however, they are underutilised in tissues and cancer models. Ribonuclease (RNase) expression is often found to be higher in complex primary tissues in comparison to cell lines. Methods used to preserve RNA during lysis often use denaturing conditions which needs to be avoided when requiring to maintain the interaction and position of the ribosome with the mRNA. Here we detail the cell lysis conditions that produce high quality RNA from several different tissues covering a range of endogenous RNase expression levels. We highlight the importance of RNA integrity for accurate determination of the global translation status of the cell as determined by polysome gradients and discuss key aspects to optimise for accurate assessment of the translatome from primary mouse tissue.

molecular biology↗

bioRxiv2022

Purine-rich RNA sequences in the 5'UTR site-specifically regulate eIF4A1-unwinding through eIF4A1-multimerisation to facilitate translation

Oncogenic translational programmes underpin cancer development and are often driven by dysregulation of oncogenic signalling pathways that converge on the eukaryotic translation initiation (eIF) 4F complex. Altered eIF4F activity promotes translation of oncogene mRNAs that typically contain highly structured 5UTRs rendering their translation strongly dependent on RNA unwinding by the DEAD-box helicase eIF4A1 subunit of the eIF4F complex. While eIF4A1-dependent mRNAs have been widely investigated, it is still unclear how highly structured mRNAs recruit and activate eIF4A1 unwinding specifically to facilitate their preferential translation. Here, we show that RNA sequence motifs regulate eIF4A1 unwinding activity in cells. Our data demonstrate that eIF4A1-dependent mRNAs contain AG-rich motifs within their 5UTR which recruit and stimulate eIF4A1 unwinding of localised RNA structure to facilitate mRNA translation. This mode of eIF4A1 regulation is used by mRNAs encoding components of mTORC-signalling and cell cycle progression and renders these mRNAs particularly sensitive to eIF4A1-inhibition. Mechanistically, we show that binding of eIF4A1 to AG-rich sequences leads to multimerization of eIF4A1 with eIF4A1 subunits performing distinct enzymatic activities. Our structural data suggest that RNA-binding of multimeric eIF4A1 induces conformational changes in the RNA substrate resulting in an optimal positioning of eIF4A1 proximal to the RNA duplex region that supports efficient unwinding. Hence, we conclude a model in which mRNAs utilise AG-rich sequences to specifically recruit eIF4A1, enabling assembly of the helicase-active multimeric eIF4A1 complex, and positioning these complexes proximal to stable localised RNA structure allowing ribosomal subunit scanning.

molecular biology↗