Mapping self-associating chromatin hubs identifies Id proteins as key determinants of exhausted CD8+ T cell fate.

Within days of exposure to chronic viral infections, activated CD8+ T cells differentiate into Tcf1-Slamf6loTim3hi exhaustion-prone effector T (TEX_EFF) cells or self-renewing Tcf1+Slamf6hiTim3lo precursor exhausted T (TPEX) cells. Here we showed that early CD8+ TEX cell fates were imprinted by forming subset-specific, self-associating chromatin hubs. Chromatin hub assembly coincided with effector or stemness gene induction and identified the transcription cofactors Id2 and Id3 as key regulators that promoted CD8+ TEX_EFF and CD8+ TPEX cell fates, respectively. Id2 drove CD8+ TEX_EFF cell specification by activating effector genes, while suppressing genes involved in exhaustion and stemness. In contrast, Id3-repressed effector genes but upregulated IL-7Rα and AhR, thereby maintaining the CD8+ TPEX cell pool. Mechanistically, Id2 and Id3 exhibited a distinct impact on the chromatin accessibility landscape in early CD8+ TEX cells by engaging Runx3 and Tcf1 transcription factors along with E proteins. These findings indicated that reshaping chromatin architecture represents a critical means for specifying CD8+ TEX cell fates and ensuring lineage stability.