De novo assembly of nuclear stress bodies rearranges and enhances NFIL3 to restrain acute inflammatory responses.

The membrane-less nuclear stress bodies (nSBs), with satellite III (SatIII) RNAs as the hallmark, are present in primates upon sensing stresses. We report that SatⅢ DNAs, SatⅢ RNAs, and 30 nSB proteins assemble into well-organized structures shortly after stresses. The activated SatⅢ heterochromatin loci rapidly expand, resulting in reduced spatial distance and enhanced expression of adjacent genes, including the transcription suppressor NFIL3, which is known to dampen proinflammatory cytokine production. Rearranging NFIL3 loci within the nSB territory enhances NFIL3 chromatin accessibility and makes NFIL3 promoters more accessible to transcription factors heat shock transcription factor 1 (HSF1) and bromodomain containing 4 (BRD4), which are also recruited to nSBs upon stresses. Human peripheral blood mononuclear cell (PBMC)-derived macrophages under heat shock plus pathogen-associated molecular pattern treatments exhibit increased SatⅢ and NFIL3 expression, the latter of which suppresses key inflammatory cytokines. Importantly, NFIL3 expression positively correlates with SatⅢ activation in septic patients, a process positively correlated to patient survival, highlighting a role of nSBs in restraining inflammatory responses.