Targeting histone acetylation dynamics and oncogenic transcription by catalytic P300/CBP inhibition

To separate causal effects of histone acetylation on chromatin accessibility and transcriptional output, we used integrated epigenomic and transcriptomic analyses following acute inhibition of major cellular lysine acetyltransferases P300 and CBP in hematological malignancies. We found that catalytic P300/CBP inhibition dynamically perturbs steady-state acetylation kinetics and suppresses oncogenic transcriptional networks in the absence of changes to chromatin accessibility. CRISPR-Cas9 screening identified NCOR1 and HDAC3 transcriptional co-repressors as the principal antagonists of P300/CBP by counteracting acetylation turnover kinetics. Finally, deacetylation of H3K27 provides nucleation sites for reciprocal methylation switching, a feature that can be exploited therapeutically by concomitant KDM6A and P300/CBP inhibition. Overall, this study indicates that the steady-state histone acetylation-methylation equilibrium functions as a molecular rheostat governing cellular transcription that is amenable to therapeutic exploitation as an anticancer regimen.

Automated summary

The study found that catalytic inhibition of P300/CBP dynamically disrupts steady-state acetylation kinetics and suppresses oncogenic transcriptional networks without changing chromatin accessibility. CRISPR-Cas9 screening identified NCOR1 and HDAC3 as the key antagonists of P300/CBP by counteracting acetylation turnover kinetics. Deacetylation of H3K27 provides nucleation sites for reciprocal methylation switching, which can be therapeutically exploited by simultaneous KDM6A and P300/CBP inhibition.