Rosa-Mercado, N. A. | Search bioRxiv

bioRxiv2026

SERBP1 is a master regulator of ribosome interactions

Ribosome function depends on interactions with diverse proteins whose activities determine translational efficiency, impose quality control and activate signaling pathways. These many competing activities must in turn be regulated. SERBP1 is an abundant cellular factor that interacts with ribosomes at multiple functionally critical sites on both dormant and active ribosomes. Here, we perform mass spectrometry across sucrose gradients in untreated and stressed cells and find that SERBP1 modulates ribosome interactions with many factors involved in processes including mRNA degradation, translational control, ribosome quality control and ribosome degradation. We then define the role of SERBP1 in protection of ribosomes against selective 40S degradation in the context of mTOR inhibition through its competition with the E3 ligase RNF10 and the atypical kinase RIOK3. Our work reveals SERBP1 as a key player in maintaining ribosome subunit balance and more broadly in the regulation of diverse ribosome activities.

molecular biology↗

bioRxiv2020

Hyperosmotic stress induces downstream-of-gene transcription and alters the RNA Polymerase II interactome despite widespread transcriptional repression

SummaryStress-induced readthrough transcription results in the synthesis of thousands of downstream-of-gene (DoG) containing transcripts. The mechanisms underlying DoG formation during cellular stress remain unknown. Nascent transcription profiles during DoG induction in human cell lines using TT-TimeLapse-seq revealed that hyperosmotic stress induces widespread transcriptional repression. Yet, DoGs are produced regardless of the transcriptional level of their upstream genes. ChIP-seq confirmed that the stress-induced redistribution of RNA Polymerase (Pol) II correlates with the transcriptional output of genes. Stress-induced alterations in the Pol II interactome are observed by mass spectrometry. While subunits of the cleavage and polyadenylation machinery remained Pol II-associated, Integrator complex subunits dissociated from Pol II under stress conditions. Depleting the catalytic subunit of the Integrator complex, Int11, using siRNAs induces hundreds of readthrough transcripts, whose parental genes partially overlap those of stress-induced DoGs. Our results provide insights into the mechanisms underlying DoG production and how Integrator activity influences DoG transcription.In brief Rosa-Mercado et al. report that hyperosmotic stress causes widespread transcriptional repression in human cells, yet DoGs arise regardless of the transcriptional response of their upstream genes. They find that the interaction between Pol II and Integrator is disrupted by hypertonicity and that knocking down the Integrator nuclease leads to DoG production.HighlightsHyperosmotic stress triggers transcriptional repression of many genes.DoG RNAs arise independent of the transcriptional level of their upstream gene.The interaction between Pol II and Integrator subunits decreases after salt stress.Depletion of the Int11 nuclease subunit induces the production of hundreds of DoGs.Competing Interest StatementThe authors have declared no competing interest.View Full Text

molecular biology↗