EXTRA-seq: a genome-integrated extended massively parallel reporter assay to quantify enhancer-promoter communication
Precise control of gene expression is essential for cellular function, but the mechanisms by which enhancers communicate with promoters to coordinate this process are not fully understood. While sequence-based deep learning models show promise in predicting enhancer-driven gene expression, experimental validation and human-interpretable mechanistic insights lag behind. Here, we present EXTRA-seq, a novel EXTended Reporter Assay followed by sequencing designed to quantify enhancer activity in endogenous contexts over kilobase-scale distances. We demonstrate that EXTRA-seq can be targeted to disease-relevant loci and captures expression changes at the resolution of individual transcription factor binding sites, enabling mechanistic discovery. Using engineered synthetic enhancer-promoter combinations, we reveal that the TATA-box acts as a dynamic range amplifier, modulating expression levels in function of enhancer strength. Importantly, we find that integrating state-of-the-art deep learning models with plasmid-based enhancer assays improves the prediction of gene expression as measured by EXTRA-seq. These findings open new avenues for predictive modeling and therapeutic applications. Overall, our work provides a powerful experimental platform to interrogate the complex interplay between enhancers and promoters, bridging the gap between in silico predictions and human-interpretable biological mechanisms.