Transcriptional cofactors display core promoter class-specificity in human

Transcriptional cofactors communicate regulatory cues from enhancers to promoters and are central effectors of transcription activation and gene expression, which is a hallmark of all multicellular organisms. However, the extent to which different cofactors display intrinsic specificity for distinct promoters is unclear. Testing intrinsic COF – core promoter (CP) compatibilities requires the systematic assessment of transcriptional activation for many CPs in the presence or absence of a given COF in an otherwise constant standardized reporter system. We therefore combined a plasmid-based high-throughput reporter assay, Self-Transcribing Active Core Promoter-sequencing (STAP-seq), with the specific recruitment of individual COFs to create a high-throughput activator bypass-like assay. Using this assay, we tested whether 5 different individually tethered human COFs (MED15, BRD4, EP300, MLL3 and EMSY) activate transcription from a selection of 12,000 candidate sequences encompassing different types of gene core promoters, enhancers and control sequences. In addition, we used the strong transcriptional activator P65 as a positive control and GFP as a negative control. We found that different COFs preferentially activate different CPs. For instance, MED15 prefers TATA-box containing CPs, while MLL3 preferentially activates CpG island promoters. The observed compatibilities between cofactors and promoters can explain how different enhancers specifically activate distinct sets of genes or alternative promoters within the same gene, and may underlie distinct transcriptional programs in human cells. Overall design: STAP-seq upon recruitment of individual transcriptional cofactor in HCT116 cells with 5 different cofactors and 2 controls, each in biological triplicate.

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Haberle V, Arnold CD, Pagani M, Rath M, Schernhuber K, Stark A