Together, these data indicate that PARP1 co-regulates activity of promoter-bound BRG1–EP300 complexes, and that poly-ADP-ribosylation of EP300 is required to enable the BRG1-dependent eviction of acetylated nucleosome, and therefore the transcription of genes involved in key intracellular processes, such as cell division and the removal of DNA damage in breast cancer cells. This evidence concerns the gene SMARCA4 and breast carcinoma.