Ribosomal RNA transcription regulates splicing through ribosomal protein RPL22

Area of Science:

• Molecular Biology
• Cancer Biology
• Genetics

Background:

• Ribosome biosynthesis is a key vulnerability in cancer, targeted by inhibiting RNA polymerase I (Pol I) transcription.
• Understanding the mechanisms of sensitivity to Pol I inhibitors is crucial for developing effective cancer therapies.

Purpose of the Study:

• To identify drivers of sensitivity to Pol I inhibitors.
• To elucidate the mechanistic link between ribosome synthesis and mRNA splicing.
• To uncover novel tumor suppressive pathways activated by Pol I inhibition.

Main Methods:

• Integration of multi-omics and drug response data from a large cancer cell panel.
• Development and application of specific Pol I inhibitors.
• Analysis of protein-RNA interactions and mRNA splicing.
• Genetic and chemical inhibition of rRNA synthesis.

Main Results:

• RPL22 frameshift mutations were identified as conferring sensitivity to Pol I inhibitors.
• RPL22 was found to directly interact with 28S rRNA and mRNA splice junctions, functioning as a splicing regulator.
• RPL22 deficiency, exacerbated by 28S rRNA sequestration, promotes splicing of RPL22L1 and MDM4.
• Inhibition of rRNA synthesis broadly remodels mRNA splicing, affecting hundreds of targets.
• RPL22-dependent alternative splicing is reversed by Pol I inhibition, revealing a novel tumor suppressive pathway.

Conclusions:

• A robust mechanism linking rRNA synthesis to mRNA splicing, coordinated by RPL22, has been uncovered.
• Pol I inhibition activates a non-canonical ribotoxic stress pathway with tumor suppressive functions.
• RPL22 mutations represent a potential biomarker for Pol I inhibitor sensitivity in cancer treatment.