Role of nuclear localization in the regulation and function of T-bet and Eomes in exhausted CD8 T cells

The transcription factors T-bet and Eomesodermin (Eomes) regulate CD8 T cell exhaustion through undefined mechanisms. Here, we show that the subcellular localization of T-bet and Eomes dictate their regulatory activity in exhausted T cells (T EX s). T EX s had a higher ratio of nuclear Eomes:T-bet than memory T cells (T MEM s) during chronic lymphocytic choriomeningitis virus (LCMV) infection in preclinical cancer models and in human tumors. Biochemically, T-bet and Eomes compete for the same DNA sequences, including the Pdcd1 T-box. High nuclear T-bet strongly represses Pdcd1 transcription in T MEM , whereas low nuclear T-bet in T EX leads to a dominant effect of Eomes that acts as a weaker repressor of Pdcd1 . Blocking PD-1 signaling in T EX s increases nuclear T-bet, restoring stronger repression of Pdcd1 , and driving T-bet-associated gene expression programs of chemotaxis, homing, and activation. These data identify a mechanism whereby the T-bet-Eomes axis regulates exhaustion through their nuclear localization, providing insights into how these transcription factors regulate T EX biology.