Make the right measurement: Discovery of an allosteric inhibition site for p300-HAT

Histone acetyltransferases(HATs) and histone deacetylases(HDACs) catalyze the dynamic and reversible acetylation of proteins, an epigenetic regulatory mechanism associated with multiple cancers. Indeed, HDAC inhibitorsare already approved in the clinic. The HAT paralogs p300 and CREB-binding protein(CBP) have been implicated in human pathologicalconditions including several hematological malignanciesand androgen receptor-positive prostate cancer. Others have reported CoA-competitive inhibitors of p300 and CBP with cell-based activity. Here, we describe 2 compounds, CPI- 076and CPI-090, discovered through p300-HAT high throughput screeningscreening, which inhibit p300-HAT via binding at an allosteric site. We present the high resolution (1.7 and 2.3 A) co-crystal structures of these molecules bound to a previously undescribed allosteric site of p300-HAT. Derivatization yielded actionable structure-activity relationships, but the full-length enzymatic assay demonstrated that this allosteric HAT inhibitor series was artifactual, inhibiting only the HAT domain of p300 with no effect on the full-length enzyme.Histone acetyltransferases(HATs) and histone deacetylases(HDACs) catalyze the dynamic and reversible acetylation of proteins, an epigenetic regulatory mechanism associated with multiple cancers. Indeed, HDAC inhibitorsare already approved in the clinic. The HAT paralogs p300 and CREB-binding protein(CBP) have been implicated in human pathologicalconditions including several hematological malignanciesand androgen receptor-positive prostate cancer. Others have reported CoA-competitive inhibitors of p300 and CBP with cell-based activity. Here, we describe 2 compounds, CPI- 076and CPI-090, discovered through p300-HAT high throughput screeningscreening, which inhibit p300-HAT via binding at an allosteric site. We present the high resolution (1.7 and 2.3 A) co-crystal structures of these molecules bound to a previously undescribed allosteric site of p300-HAT. Derivatization yielded actionable structure-activity relationships, but the full-length enzymatic assay demonstrated that this allosteric HAT inhib...