FIG. 11.

EID-1 inhibits p300 HAT activity. To determine if EID-1 inhibited HAT activity, immunoprecipitated p300 was incubated with purified histones and [¹⁴C]acetyl coenzyme A. Complexes were resolved by SDS-PAGE and subjected to autoradiography. (A) Purified GST or GST–EID-1 was added to the indicated reaction mixtures, and the effect on p300 HAT activity was determined. (B) Cardiac myocytes were infected with the indicated viruses. Thirty-six hours after infection, cells were exposed to ³H-Na acetate for 1 h. Total protein lysates were harvested in lysate buffer plus 10 mM Na butyrate, and p300 was immunoprecipitated. Shown are autoradiograms documenting p300 autoacetylation in vivo. One-tenth of the immunoprecipitated complexes was probed for total p300 expression to ensure that results were not related to EID-1 effects on total p300 levels. (C) Purified Flag peptide or Flag fusion proteins (80 pmol) were coincubated with the HAT assay mixture to determine the domains within EID-1 that mediate this inhibitory effect.