Biology subjects

Raval, M.

Publications and source records attributed to Raval, M..

4 recordsLinked to original sources

bioRxiv2026

Anticodon nucleotide modifications affect translational tuning by the ribosomal CAR surface

Nucleotide modifications of the tRNA anticodon can affect protein translation fidelity and speed. Chemical modifications of the anticodon nucleotide 34 are regulated under cellular stress and associated with several translational defects and pathologies. Here, we investigate how these modifications influence A-site codon recognition interactions and their coupling to the CAR site that lies adjacent to nucleotide 34 in the ribosome. The conserved three-residue CAR interface hydrogen bonds in a sequence-dependent manner to the mRNA +1 codon 3-adjacent to the A-site codon and is implicated in tuning translational speed. The C of CAR is pi-stacked with the nucleotide 34 of the A site tRNA anticodon. The A site and the CAR site influence each others hydrogen bonding and stacking interactions, and these codon-adjacency effects potentially provide a layer of regulation affecting translational fidelity and kinetics. Through molecular dynamics simulations of a subsystem of a translocating ribosome IRES-model, we observed that nucleotide 34 modifications affect the hydrogen bonding and stacking interactions at the A site and CAR site as well as CARs influence on the A site interactions. Integrating these results with gene sequence and ribosome profiling analyses, we propose that nucleotide 34 modifications help modulate CARs sequence-dependent tuning of translation in response to cellular stress. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/740946v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@1971867org.highwire.dtl.DTLVardef@c31822org.highwire.dtl.DTLVardef@6597f6org.highwire.dtl.DTLVardef@1dbd747_HPS_FORMAT_FIGEXP M_FIG C_FIG

systems biology↗

bioRxiv2026

Interplay of the ribosome A and CAR sites

Protein translation is a highly regulated process influenced by multiple factors at the initiation, elongation, and termination stages. One notable regulatory element of the ribosome is the CAR interaction surface, a three-residue motif in the structure of the ribosome composed of C1274 and A1427 of S. cerevisiae 18S rRNA (corresponding to C1054 and A1196 in E. coli 16S rRNA) and R146 of ribosomal protein Rps3. CAR is highly conserved and positioned adjacent to the amino-acyl (A site) decoding center. It establishes hydrogen bonds with the +1 codon next in line to enter the ribosome A site, acting as an extension of the tRNA anticodon and forming base-stacking interactions with nucleotide 34 of the tRNA. However, despite CARs enzymatically strategic positioning within the ribosome, its functional relationship with the A site remains poorly characterized. Using molecular dynamics (MD) simulations, we examined the interplay between the A site and CAR site, revealing sequence-dependent modulation of H-bonding and {pi}-stacking interactions within and between the two sites. These findings highlight the interplay between the A site and CAR site, suggesting a structural and functional connection between these two regions of the ribosome that may contribute to mRNA sequence-specific tuning of translation elongation. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=91 SRC="FIGDIR/small/714784v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@1919efaorg.highwire.dtl.DTLVardef@15c4882org.highwire.dtl.DTLVardef@19c7782org.highwire.dtl.DTLVardef@16a1246_HPS_FORMAT_FIGEXP M_FIG C_FIG

systems biology↗

bioRxiv2024

GNN codon adjacency regulates protein translation

The central dogma treats the ribosome as a molecular machine that reads one mRNA codon at a time as it adds each amino acid to its growing peptide chain. However, this and previous studies suggest that ribosomes actually perceive pairs of adjacent codons as they take three-nucleotide steps along the mRNA. We examined GNN codons which we find are surprisingly overrepresented in eukaryote protein-coding open reading frames (ORFs), especially immediately after NNU codons. Ribosome profiling experiments in yeast revealed that ribosomes with NNU at their aminoacyl (A) site have particularly elevated densities when NNU is immediately followed (3) by a GNN codon, indicating slower mRNA threading of the NNU codon from the ribosomes A to peptidyl (P) sites. Moreover, if the assessment was limited to ribosomes that have only recently arrived at the next codon, by examining 21-nucleotide ribosome footprints (21-nt RFPs), elevated densities were observed for multiple codon classes when followed by GNN. This striking translation slowdown at adjacent 5-NNN GNN codon pairs is likely mediated in part by the ribosomes CAR surface which acts as an extension of the A-site tRNA anticodon during ribosome translocation and interacts through hydrogen bonding and pi stacking with the GNN codon. The functional consequences of 5-NNN GNN codon adjacency are expected to influence the evolution of protein coding sequences. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=78 SRC="FIGDIR/small/583757v1_ufig1.gif" ALT="Figure 1"> View larger version (13K): org.highwire.dtl.DTLVardef@d29087org.highwire.dtl.DTLVardef@e8f7dorg.highwire.dtl.DTLVardef@1ee5792org.highwire.dtl.DTLVardef@b750fb_HPS_FORMAT_FIGEXP M_FIG Graphical abstract C_FIG

molecular biology↗

bioRxiv2022

The CAR mRNA-Interaction Surface is a Zipper Extension of the Ribosome A Site

The ribosome CAR interaction surface behaves like an extension of the decoding center A site and has H-bond interactions with the +1 codon that is next in line to enter the A site. Through molecular dynamics simulations, we investigated the codon sequence specificity of this CAR-mRNA interaction and discovered a strong preference for GCN codons, suggesting that there may be a sequence-dependent layer of translational regulation dependent on the CAR interaction surface. Dissection of the CAR-mRNA interaction through nucleotide substitution experiments showed that the first nucleotide of the +1 codon dominates over the second nucleotide position, consistent with an energetically favorable zipper-like activity that emanates from the A site through the CAR-mRNA interface. The +1 codon/CAR interaction is also affected by the identity of nucleotide 3 of +1 GCN codons which influences the stacking of G and C. Clustering analysis suggests that the A site decoding center adopts different neighborhood substates that depend on the identity of the +1 codon.

biophysics↗