Current models posit that nuclear speckles (NSs) serve as reservoirs of splicing factors and facilitate posttranscriptional mRNA processing. Here, we discovered that ribotoxic stress induces a profound reorganization of NSs with enhanced recruitment of factors required for splice-site recognition, including the RNA-binding protein TIAR, U1 snRNP proteins and U2-associated factor 65, as well as serine 2 phosphorylated RNA polymerase II. NS reorganization relies on the stress-activated p38 mitogen-activated protein kinase (MAPK) pathway and coincides with splicing activation of both pre-existing and newly synthesized pre-mRNAs. In particular, ribotoxic stress causes targeted excision of retained introns from pre-mRNAs of immediate early genes (IEGs), whose transcription is induced during the stress response. Importantly, enhanced splicing of the IEGs ZFP36 and FOS is accompanied by relocalization of the corresponding nuclear mRNA foci to NSs. Our study reveals NSs as a dynamic compartment that is remodeled under stress conditions, whereby NSs appear to become sites of IEG transcription and efficient cotranscriptional splicing.
Stress-induced nuclear speckle reorganization is linked to activation of immediate early gene splicing
Disclosures: The authors declare no competing interests exist.
- Award Id(s): SRP34
- Award Id(s): TRR 186,TRR 319,GRK 2727,SFB 1190,SPP 1935
Hsu-Min Sung, Johanna Schott, Philipp Boss, Janina A. Lehmann, Marius Roland Hardt, Doris Lindner, Joris Messens, Ivan Bogeski, Uwe Ohler, Georg Stoecklin; Stress-induced nuclear speckle reorganization is linked to activation of immediate early gene splicing. J Cell Biol 4 December 2023; 222 (12): e202111151. doi: https://doi.org/10.1083/jcb.202111151
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