bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2022.08.14.503931

Dynamic Phosphorylation Regulates Eukaryotic Translation Initiation Factor 4A Activity During the Cell Cycle

Sahoo, A.·Zollo, R. A.·Shen, S.·Ashraf, M.·Nelson, S.·Koudelka, G. B.·Qu, J.·Barbi, J.·Walker, S. E.
View original source ↗Export metadata ↓

Abstract

The eukaryotic translation initiation factor 4A (eIF4A) resolves mRNA structures to support protein synthesis, yet little is known about its regulation. Here we analyzed eIF4A phosphorylation during alternate stages of the cell cycle, and found three residues near the DEAD box motif (T73, T146, and S177) underwent substantial phosphorylation changes. Phosphomimetic mutations T73D and T146D led to G2/M phase arrest, and abolished eIF4A interaction with RNA, suggesting eIF4A activity is needed for completion of cell division. In addition to these repressive events, we found that S177, a site immediately adjacent to the DEAD-box, showed diametrically opposed phosphorylation, with only phosphorylated S177 present during G1/S arrest and dephosphorylated S177 peptides during G2/M arrest. Phosphomimetic S177D eIF4A increased polysome levels and enhanced normally reduced eIF4A-eIF4G-interaction during G2/M, while phosphodeficient S177A decreased polysome levels and reduced growth, suggesting phosphorylation of S177 enhances eIF4A-mediated translation during G1/S. Together these results suggest that dynamic phosphorylation of eIF4A S177 serves to stimulate translation during G1/S, while inhibitory phosphorylation of additional sites holds the potential to rapidly transition eIF4A to an inactive state and turn off translation. These results also suggest an important role for eIF4A in coupling translation to cell cycle stages.

Explore related subjects

molecular biologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Sahoo, A., Zollo, R. A., Shen, S., Ashraf, M., Nelson, S., Koudelka, G. B., Qu, J., Barbi, J., Walker, S. E.. 2022-08-20. Dynamic Phosphorylation Regulates Eukaryotic Translation Initiation Factor 4A Activity During the Cell Cycle. https://doi.org/10.1101/2022.08.14.503931

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Engineered Miniature ParTasR Enables Efficient PAMless Genome Editing

TIGR-Tas system holds great promise for genome-engineering applications owing to its compact size and PAMless targeting capability. However, its low editing efficiency in mammalian cells severely limits its broader utility. Here, we engineered a highly active variant of ParTasR, termed eTasR, through structure-guided rational design of ParTasR combined with fusion to the exonuclease TREX2. eTasR increased mammalian editing efficiency from the original 4.29% to 48.94% with an average 26.52-fold increase, significantly surpassing the efficiency of SpRY, a reported version of PAM-free nuclease. More importantly, single-AAV delivery enabled efficient Hpd disruption in vivo, resulting in robust phenotypic rescue. Thus, eTasR provides a compact, PAMless and highly efficient platform for genome editing and therapeutic applications.

molecular biology↗
bioRxiv2026

Enhancing pancreatic islet cell survival via NMDAR antagonist-driven ROR1 activation as revealed by phosphoproteomics

NMDA receptors (NMDARs) control function and survival not only of neurons, but also of insulin-producing pancreatic beta cells. Since insufficient insulin secretion and beta cell death are key events during diabetes development, targeting NMDARs offers a therapeutic approach. Specifically, the NMDAR antagonist dextrorphan (DXO) increases glucose-stimulated insulin secretion in clinical trials. Furthermore, treatment with DXO or optimized DXO derivatives prevents pancreatic islet cell death upon diabetogenic insults. Nonetheless, the signaling pathways induced by NMDAR inhibition are poorly understood. Here, we use complementary approaches, phosphoproteomics and tyrosine kinase profiling, to demonstrate that DXO and its derivatives rapidly regulate multiple intracellular signaling clusters, including mTOR and ERK signaling, in pancreatic islets. Notably, mTOR inhibition, but not ERK inhibition, is sufficient to negate DXO's protective effects. Further, we show that activation of Receptor Tyrosine Kinase-like Orphan Receptor 1 (ROR1) is a universal event upon NMDAR inhibition in islets. Simultaneous knockdown of Ror1/ROR1 and its paralogue Ror2/ROR2 compromises the viability of both mouse and human islets, highlighting the ROR1/2 signaling axis as a promising avenue for enhancing beta cell survival.

molecular biology↗
bioRxiv2026

An ssRNA Phage Single-gene Lysis Protein Targeting MraY Reveals Convergent Evolution Across the RNA-DNA Phage Boundary

Small lytic phages of the ssRNA Leviviricetes and ssDNA Microviricetes achieve host lysis by expression of a single protein, designated as an Sgl protein. Four ssRNA Sgls have been shown to inhibit steps in peptidoglycan biosynthesis: three target MurJ, the Lipid II flippase, and one targets MurA, the committed step of the pathway. A fifth Sgl, the E protein of the canonical ssDNA microvirus {varphi}X174, inhibits MraY, which catalyzes the synthesis of the first lipid-linked intermediate. This inhibition requires SlyD, a cytoplasmic FKBP-type peptidyl-prolyl cis-trans isomerase. The Sgl of the Caulobacter ssRNA phage {varphi}Cb5 (Cebevirus halophobicum) has not been characterized. Here, we present physiological evidence that Sgl{varphi}Cb5 targets MraY. Moreover, we show that, despite the absence of detectable sequence similarity, Sgl{varphi}Cb5 shares several features with the {varphi}X174 E protein, including the distribution of hydrophobic and charged residues, a proposed N-out, C-in membrane topology, and retention of lytic activity in an Sgl{varphi}Cb5 -LacZ fusion. Furthermore, expression of the Caulobacter cytoplasmic FKBP-type peptidyl-prolyl cis-trans isomerase CC2799 enhances Sgl{varphi}Cb5 -mediated lysis in E. coli. These parallels between Sgl function in a DNA phage and an RNA phage either represent remarkably consonant convergent evolution or some evolutionary cross-over event for which there is currently no precedent.

molecular biology↗