Cancer mutations inhibit the coactivator activity of p300 core

p300 is an important transcription coactivator that enhances gene expression by acetylating histones through its catalytic core domain. p300 is mutated in some cancers, and cancer mutations in the histone acetyltransferase (HAT) domain can inactivate the coactivator function of the protein. However, many mutations in the p300 catalytic core that have been observed in human tumors have not been characterized for functional effects on p300 coactivator activity. The goal of this study was to screen cancer mutations using a previously published system in which the p300 catalytic core is fused to deactivated Cas9 (p300core‐dCas9). Cancer mutations in the bromodomain, PHD/RING domain, and histone acetyltransferase (HAT) domain were created in the p300core‐dCas9 protein. After the addition of guide RNA targeting p300core‐dCas9 to the promoter of a given target gene, quantitative PCR was performed to measure the coactivator function of the wild‐type and mutant proteins. Mutations in the bromodomain showed variable effects on gene expression activation, while mutations in the PHD/RING domain and HAT domain were inhibitory. These results demonstrate that cancer mutations in the p300 core can alter p300 function and provide insight into the effects of cancer mutations that occur outside of the HAT domain. Support or Funding Information Longwood University Faculty Research and Development Grant