Affinity and Dose of TCR Engagement Yield Proportional Enhancer and Gene Activity in CD4+ T Cells

Affinity and dose of T cell receptor (TCR) interaction with antigens govern the magnitude of CD4+ T cell responses, but questions remain regarding the quantitative translation of TCR engagement into downstream signals. We find that while the response of CD4+ T cells to antigenic stimulation is bimodal, activated cells exhibit analog responses proportional to signal strength. Gene expression output reflects TCR signal strength, providing a signature of T cell activation. Expression changes rely on a pre-established enhancer landscape and quantitative acetylation at AP-1 binding sites. Finally, we show that graded expression of activation genes depends on ERK pathway activation, suggesting that an ERK-AP-1 axis translates TCR signal strength into proportional activation of enhancers and genes essential for T cell function. CD4+ T cells from transgenic AND mice were sequenced under the conditions indicated. Replicates are included for each type of data (RNA-Seq, ChIP-Seq), and are numbered accordingly. The No Peptide condition serves as the untreated control for the peptide-treated samples, and inputs are provided for ChIP-Sequencing samples.