Chemical Dissection of the Super Elongation Complex

The proposal Chemical Dissection of the Super Elongation Complex is a cross- disciplinary approach geared to use pharmacologic and chemical-genetics approaches to probe and understand the super elongation complex (SEC). The SEC is a dynamic multi- protein assembly that orchestrates transcription elongation via differential P-TEFb recruitment to enable target-gene specific release of paused Pol II. Different lines of evidence point to a functional relevance of the SEC in human cancer by establishing aberrant transcription elongation to drive transcriptional programs that sustain cellular growth, counteract differentiation or that permit adaptions to the tumor microenvironment. However, a precise understanding of the regulatory architecture of how individual SEC subunits control and permit target-specific elongation control is lacking. This is due to the limited kinetic resolution provided by common genetic perturbation strategies as well as a lack of well-defined small-molecules that can interfere with SEC subunits. To overcome these limitations, we will devise target protein degradation as a means to acute SEC disruption, and couple acute perturbations with holistic measurements of gene expression, complex stoichiometry and chromatin structure. This will allow us to derive a systems-level understanding of how different subunits contribute to the overall role of the SEC in gene activity. Moreover, we will deploy innovative screening technology that allows us to test close to 100000 small- molecule probes for their capacity to interfere with the SEC component ENL in cancer cells. This will be coupled with downstream target-identification strategies and in-depth mechanistic validation of the molecular mechanism of action of identified small-molecule hits. We expect this research to result in well characterized chemical probes, which are expected to serve as a scalable vector to the study of transcription elongation and especially the SEC in cancer, development and homeostasis.