Fig. 3: SIPAN are induced by metabolic stress and do not correspond to previously known nuclear structures.

a PSMD11 or PSMD4 proteasome foci do not correspond to any known nuclear foci, structure or bodies including PML bodies (PML staining), nuclei (Fibrillarin staining), nuclear speckles (SC35 staining) or DNA double strand break foci (53BP1 staining). Stainings were conducted following 6 hrs incubation in HBSS (representative from 3 independent experiments). b Confocal microscopy showing PSMB4-GFP foci in low-density chromatin regions (representative from 3 independent experiments). c Transmission electronic microscopy in conjunction with colloidal gold-based immunodetection of PSMD4. Following incubation of IMR90 cells in HBSS for 6 hrs, cells were fixed and processed for immunodetection and electronic microscopy analysis. PSMD4 condensates are membrane-less and located in regions with reduced chromatin density (representative from 2 independent experiments). d Ribosomal proteins do not co-localize with proteasome foci. Merges from Supplementary Fig. 3b–d. Graphs at the right represent relative signal intensity of the indicated line for each component of proteasome (representative from 2 independent experiments). e, f Proteasome foci are not observed in response to other stress conditions. e IMR90 cells were treated with various chemical or physical agents and endogenous PSMD4 was detected by immunostaining at the indicated times (n = 3 independent experiments). f Western blot analysis of proteins following treatments of cells shown in (e) to ensure treatment efficacy (representative from 2 independent experiments). Data in (e) represent the mean ± SD. Source data are provided as a Source data file.