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• Heat stress is a major limiting factor for global wheat production and causes dramatic yield loss worldwide. The TaMBF1c gene is upregulated in response to heat stress in wheat. Understanding the molecular mechanisms associated with heat stress responses will pave the way to improve wheat thermotolerance. • Through CRISPR/Cas9-based gene editing, polysome profiling coupled with RNA-sequencing analysis, and protein–protein interactions, we show that TaMBF1c conferred heat response via regulating a specific gene translation in wheat. • The results showed that TaMBF1c is evolutionarily conserved in diploid, tetraploid and hexaploid wheat species, and its knockdown and knockout lines show increased heat sensitivity. TaMBF1c is colocalized with the stress granule complex and interacts with TaG3BP. TaMBF1c affects the translation efficiency of a subset of heat responsive genes, which are significantly enriched in the ‘sequence-specific DNA binding’ term. Moreover, gene expression network analysis demonstrated that TaMBF1c is closely associated with the translation of heat shock proteins. • Our findings reveal a contribution of TaMBF1c in regulating the heat stress response via the translation process, and provide a new target for improving heat tolerance in wheat breeding programs.

Deregulation of mRNA translation is a widespread characteristic of glioblastoma (GBM), aggressive malignant brain tumors that are resistant to conventional therapies. RNA-binding proteins (RBPs) play a critical role in translational regulation, yet the mechanisms and impact of these regulations on cancer development, progression and response to therapy remain to be fully understood. Here, we showed that hnRNP H/F RBPs are potent regulators of translation through several mechanisms that converge to modulate the expression and/or the activity of translation initiation factors. Among these, hnRNP H/F regulate the phosphorylation of eIF4E and its translational targets by controlling RNA splicing of the A-Raf kinase mRNA, which in turn modulates the MEK-ERK/MAPK signaling pathway. The underlying mechanism involves RNA G-quadruplex (RG4s), RNA structures whose modulation phenocopies hnRNP H/F translation regulation in GBM cells. Our results highlighted that hnRNP H/F are essential for key functional pathways regulating proliferation and survival of GBM, highlighting its targeting as a promising strategy for improving therapeutic outcomes.

In all kingdoms of life, proteins are synthesized by ribosomes in a process referred to as translation. The amplitude of translational regulation exceeds the sum of transcription, mRNA degradation and protein degradation. Therefore, it is essential to investigate translation in a global scale. Like the other “omics”-methods, translatomics investigates the totality of the components in the translation process, including but not limited to translating mRNAs, ribosomes, tRNAs, regulatory RNAs and nascent polypeptide chains. Technical advances in recent years have brought breakthroughs in the investigation of these components at global scale, both for their composition and dynamics. These methods have been applied in a rapidly increasing number of studies to reveal multifaceted aspects of translation control. The process of translation is not restricted to the conversion of mRNA coding sequences into polypeptide chains, it also controls the composition of the proteome in a delicate and responsive way. Therefore, translatomics has extended its unique and innovative power to many fields including proteomics, cancer research, bacterial stress response, biological rhythmicity and plant biology. Rational design in translation can enhance recombinant protein production for thousands of times. This brief review summarizes the main state-of-the-art methods of translatomics, highlights recent discoveries made in this field and introduces applications of translatomics on basic biological and biomedical research.

Background Polysome profiling is a widespread technique to study mRNA translation. After separation of cellular particles by ultracentrifugation on a sucrose-density gradient, a UV absorbance profile is recorded during elution, which mostly reflects RNA content and shows distinct peaks for ribosomal subunits, monosomes and polysomes with increasing number of ribosomes. This profile can be used to assess global translational activity, or to reveal changes in ribosome biogenesis and translation elongation. In addition, it is also possible to measure the association of fluorescently tagged proteins with ribosomal subunits or polysomes. Alignment and quantification of polysome profiles usually relies on spreadsheet programs, custom R/Python scripts or commercial software. Results With QuAPPro, we present the first interactive web app that allows quantification and alignment of polysome profiles, independently of the device or software that was used to generate the profiles. QuAPPro was written in R, with a graphical user interface implemented in R shiny. It supports interactive visualization and analysis of polysome profiles, including profile smoothing, baseline selection, alignment along a defined point on the x-axis, quantification of profile subsections and deconvolution for resolving individual peaks. Fluorescence profiles can be aligned and quantified in parallel. Finally, quantification results can be summarized and visualized as bar plots. Every interactive plot can be exported directly in a publication-ready format. Conclusions This user-friendly tool does not only speed up the analysis of polysome profiles but also facilitates reproducibility and documentation of the process, without the need for programming abilities or commercial software.

Ribosome profiling is a powerful technique used to study gene expression on a transcriptome-wide scale. It involves sequencing of mRNA fragments protected by ribosomes from ribonuclease digestion. The initial steps commonly involve cell lysis followed by centrifugation and ribonuclease digestion. We find that centrifugation depletes 329 translated mRNAs in HEK293T cells. Many of these mRNAs encode cytoskeleton proteins. This suggests that the expression of a subset of mRNAs may be significantly underestimated in most ribosome profiling experiments. We show that omitting the centrifugation step after cell lysis can resolve this issue.

Background The RNA helicase eIF4A1 is a key component of the translation initiation machinery and is required for the translation of many pro-oncogenic mRNAs. There is increasing interest in targeting eIF4A1 therapeutically in cancer, thus understanding how this protein leads to the selective re-programming of the translational landscape is critical. While it is known that eIF4A1-dependent mRNAs frequently have long GC-rich 5′UTRs, the details of how 5′UTR structure is resculptured by eIF4A1 to enhance the translation of specific mRNAs are unknown. Results Using Structure-seq2 and polysome profiling, we assess global mRNA structure and translational efficiency in MCF7 cells, with and without eIF4A inhibition with hippuristanol. We find that eIF4A inhibition does not lead to global increases in 5′UTR structure, but rather it leads to 5′UTR remodeling, with localized gains and losses of structure. The degree of these localized structural changes is associated with 5′UTR length, meaning that eIF4A-dependent mRNAs have greater localized gains of structure due to their increased 5′UTR length. However, it is not solely increased localized structure that causes eIF4A-dependency but the position of the structured regions, as these structured elements are located predominantly at the 3′ end of the 5′UTR. Conclusions By measuring changes in RNA structure following eIF4A inhibition, we show that eIF4A remodels local 5′UTR structures. The location of these structural elements ultimately determines the dependency on eIF4A, with increased structure just upstream of the CDS being the major limiting factor in translation, which is overcome by eIF4A activity.

The synthesis of new proteins is a fundamental aspect of cellular life and is required for many neurological processes, including the formation, updating and extinction of long-term memories. Protein synthesis is impaired in neurodegenerative diseases including tauopathies, in which pathology is caused by aberrant changes to the microtubule-associated protein tau. We recently showed that both global de novo protein synthesis and the synthesis of select ribosomal proteins (RPs) are decreased in mouse models of frontotemporal dementia (FTD) which express mutant forms of tau. However, a comprehensive analysis of the effect of FTD-mutant tau on ribosomes is lacking. Here we used polysome profiling, de novo protein labelling and mass spectrometry-based proteomics to examine how ribosomes are altered in models of FTD. We identified 10 RPs which were decreased in abundance in primary neurons taken from the K3 mouse model of FTD. We further demonstrate that expression of human tau (hTau) decreases both protein synthesis and biogenesis of the 60S ribosomal subunit, with these effects being exacerbated in the presence of FTD-associated tau mutations. Lastly, we demonstrate that expression of the amino-terminal projection domain of hTau is sufficient to reduce protein synthesis and ribosomal biogenesis. Together, these data reinforce a role for tau in impairing ribosomal function.

The protein output of different mRNAs can vary by two orders of magnitude; therefore, it is critical to understand the processes that control gene expression operating at the level of translation. Translatome-wide techniques, such as polysome profiling and ribosome profiling, are key methods for determining the translation 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 need to be avoided when maintaining the interaction and position of the ribosome with the mRNA is required. 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.

Background Cell differentiation during development is orchestrated by precisely coordinated gene expression programs. While some regulatory mechanisms are well understood, there is a significant room to explore unresolved aspects of lineage choice and cell-fate decisions, as many events in these processes are still not fully elucidated. Given that, gene expression is influenced not only by transcriptional control but also by post-transcriptional events. Here, we described the presence of post-transcriptional regulation on gene expression during lineage commitment across all three embryonic germ layers. We employed monolayer differentiation protocols to map early transcriptional and post-transcriptional events in human embryonic stem cell specification. This approach included obtaining representative populations from the three germ layers, followed by sequencing of both polysome-bound and total RNAs. Results We characterized our model by its unique expression profile and the presence of specific markers for each differentiation. RNA sequencing revealed a consistent pattern of gene upregulated and downregulated when comparing the transcriptome and translatome during the differentiation of all three germ layers. By comparing these datasets, we identified genes subjected to post-transcriptional regulation in all germ layer differentiations and categorized the nature of this regulation. GO analysis demonstrated that polysome profiling serves as a complementary technique, capturing nuances that may be overlooked when analyzing only the transcriptome. Finally, we directly compared the transcriptome and translatome to identify genes actively recruited to the translation machinery, uncovering unique features specific to each germ layer. Conclusions Substantial post-transcriptional modulation was found during germ layer commitment, emphasizing the translatome potency in capturing nuanced gene expression regulation. These findings highlight the post-transcriptional regulation’s critical role in early embryonic development, offering new insights into the molecular mechanisms of cell differentiation.

miRNAs moderately inhibit the translation and enhance the degradation of their target mRNAs via cognate binding sites located predominantly in the 3′-untranslated regions (UTR). Paradoxically, miRNA targets are also polysome-associated. We studied the polysome association by the comparative translationally less-active light- and more-active heavy-polysome profiling of a wild type (WT) human cell line and its isogenic mutant (MT) with a disrupted DICER1 gene and, thus, mature miRNA production. As expected, the open reading frame (ORF) length is a major determinant of light- to heavy-polysome mRNA abundance ratios, but is rendered less powerful in WT than in MT cells by miRNA-regulatory activities. We also observed that miRNAs tend to target mRNAs with longer ORFs, and that adjusting the mRNA abundance ratio with the ORF length improves its correlation with the 3′-UTR miRNA-binding-site count. In WT cells, miRNA-targeted mRNAs exhibit higher abundance in light relative to heavy polysomes, i.e., light-polysome enrichment. In MT cells, the DICER1 disruption not only significantly abrogated the light-polysome enrichment, but also narrowed the mRNA abundance ratio value range. Additionally, the abrogation of the enrichment due to the DICER1 gene disruption, i.e., the decreases of the ORF-length-adjusted mRNA abundance ratio from WT to MT cells, exhibits a nearly perfect linear correlation with the 3′-UTR binding-site count. Transcription factors and protein kinases are the top two most enriched mRNA groups. Taken together, the results provide evidence for the light-polysome enrichment of miRNA-targeted mRNAs to reconcile polysome association and moderate translation inhibition, and that ORF length is an important, though currently under-appreciated, transcriptome regulation parameter.