Biology subjects

Tamilselvam, B.

Publications and source records attributed to Tamilselvam, B..

3 recordsLinked to original sources

bioRxiv2026

Quantitative profiling of basal and stress-induced ribosome collisions

Ribosomes stall when they encounter problematic codons or cellular stress that perturbs translation. Stalled ribosomes can lead to the formation of ribosome collisions, also known as disomes, that engage cellular surveillance and stress signaling pathways. How many disomes form during basal conditions and how disome levels change under stress remain poorly understood. Here, we used spike-in normalized Ribo-seq and Disome-seq to quantify transcriptome-wide disome levels. Applying this approach in yeast and human cells, we found that disomes comprise approximately 2-10% of translating ribosomes under basal conditions. A high-resolution Disome-seq experiment in human cells identified reproducible disome-forming sites that contribute to the basal level of disome formation in the cell. Exposure of yeast cells to methyl methanesulfonate and human cells to anisomycin increased disome abundance up to four-fold and changed the distribution of collisions in a stress-specific and context-dependent manner. Overall, these data provide a quantitative, transcriptome-wide framework for measuring disome levels and reveal how translational stress reshapes the landscape of ribosome collisions in cells.

molecular biology↗

bioRxiv2026

5-Azacytidine incorporation into mRNAs disrupts translation and induces ribosome collisions

5-Azacytidine (5-AzaC) is a cytidine analog and is widely used to treat myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). Although its therapeutic activity is primarily attributed to hypomethylation resulting from DNA incorporation, the majority of 5-AzaC is incorporated into RNA. However, the functional consequences of 5-AzaC incorporation into RNA have been unknown. Here, we show that 5-AzaC treatment of cells leads to inhibition of protein synthesis. Ribo-seq, Disome-seq, and RNA-seq in cells treated with 5-AzaC exhibit a time-dependent C-to-G transversion signature in mRNAs within 2 h of treatment. These transversion events are enriched within footprint positions corresponding to the A-site of monosomes or leading stalled ribosome in a disome complex. Consistently, ribosome and disome footprints are accumulated at sites with C-rich codons in the A-site, specifically with the codons containing a C in the second position. 5-AzaC activates the integrated stress response (ISR) and the ribotoxic stress response (RSR) in a GCN2- and ZAK-dependent manner, consistent with disome-mediated signaling. Furthermore, loss of the Ribosome Quality Control (RQC) factor, ZNF598, sensitizes cells to 5-AzaC. Collectively, our results support a model where 5-AzaC is rapidly incorporated into mRNAs, disrupts decoding, and triggers disome-mediated signaling pathways, which contribute to its cytotoxicity. These findings suggest that translation disruption represents an additional layer of 5-AzaCs mechanism of action, alongside its known DNA-mediated effects.

biochemistry↗

bioRxiv2024

Autophagy suppression in DNA damaged cells occurs through a newly identified p53-proteasome-LC3 axis

Macroautophagy is thought to have a critical role in shaping and refining cellular proteostasis in eukaryotic cells recovering from DNA damage. Here, we report a mechanism by which autophagy is suppressed in cells exposed to bacterial toxin-, chemical-, or radiation-mediated sources of genotoxicity. Autophagy suppression is directly linked to cellular responses to DNA damage, and specifically the stabilization of the tumor suppressor p53, which is both required and sufficient for regulating the ubiquitination and proteasome-dependent reduction in cellular pools of microtubule-associated protein 1 light chain 3 (LC3A/B), a key precursor of autophagosome biogenesis and maturation, in both epithelial cells and an ex vivo organoid model. Our data indicate that suppression of autophagy, through a newly identified p53-proteasome-LC3 axis, is a conserved cellular response to multiple sources of genotoxicity. Such a mechanism could potentially be important for realigning proteostasis in cells undergoing DNA damage repair.

cell biology↗