Splicing modulators elicit global translational repression by condensate-prone proteins translated from introns

Cell Chem Biol. 2022 Feb 17;29(2):259-275.e10. doi: 10.1016/j.chembiol.2021.07.015. Epub 2021 Sep 13.


Chemical splicing modulators that bind to the spliceosome have provided an attractive avenue for cancer treatment. Splicing modulators induce accumulation and subsequent translation of a subset of intron-retained mRNAs. However, the biological effect of proteins containing translated intron sequences remains unclear. Here, we identify a number of truncated proteins generated upon treatment with the splicing modulator spliceostatin A (SSA) via genome-wide ribosome profiling and bio-orthogonal noncanonical amino acid tagging (BONCAT) mass spectrometry. A subset of these truncated proteins has intrinsically disordered regions, forms insoluble cellular condensates, and triggers the proteotoxic stress response through c-Jun N-terminal kinase (JNK) phosphorylation, thereby inhibiting the mTORC1 pathway. In turn, this reduces global translation. These findings indicate that creating an overburden of condensate-prone proteins derived from introns represses translation and prevents further production of harmful truncated proteins. This mechanism appears to contribute to the antiproliferative and proapoptotic activity of splicing modulators.

Keywords: BONCAT; JNK; condensate; intron; mTORC1; proteostasis; ribosome profiling; spliceostatin A; splicing modulator; translation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Enzyme Inhibitors / pharmacology
  • Humans
  • Introns
  • JNK Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • JNK Mitogen-Activated Protein Kinases / genetics*
  • Mechanistic Target of Rapamycin Complex 1 / antagonists & inhibitors
  • Mechanistic Target of Rapamycin Complex 1 / genetics*
  • Pyrans / pharmacology
  • RNA Splicing / drug effects
  • RNA Splicing / genetics*
  • RNA-Seq
  • Spiro Compounds / pharmacology
  • Spliceosomes / drug effects
  • Spliceosomes / genetics*


  • Enzyme Inhibitors
  • Pyrans
  • Spiro Compounds
  • spliceostatin A
  • Mechanistic Target of Rapamycin Complex 1
  • JNK Mitogen-Activated Protein Kinases