ZBTB7A is a modulator of KDM5-driven transcriptional networks in basal breast cancer  (ChIP-Seq)
We previously identified KDM5B, encoding a histone H3 lysine 4 (H3K4) demethylase, as an oncogene in estrogen receptor positive (ER+) breast cancer driving endocrine resistance. Here we describe that KDM5A is frequently amplified and overexpressed in basal breast tumors and is associated with chemotherapy resistance. Using CRISPR knockout viability screens -/+  KDM5 inhibition (KDM5i), we found that deletion of the transcription factor ZBTB7A and core SAGA complex increased sensitivity to KDM5i, whereas knockout of RHO-GTPases led to resistance. Integrated ChIP-seq and RNA-seq analyses revealed colocalization of ZBTB7A and KDM5s at promoters with high H3K4me3 signal and dependence of KDM5A binding on ZBTB7A. ZBTB7A knockout had a pleiotropic effect on transcriptional responses to KDM5i, in which it modulates the KDM5i-induced innate immune signaling and NF-kB-regulated genes. ZBTB7A knockout and KDM5i cooperate to alter cell states with KDM5i decreasing basal-like and ZBTB7A knockout inducing mesenchymal-like gene expression patterns. Our work furthers our understanding of KDM5-mediated gene regulation in breast cancer and identifies key pathways that mediate sensitivity to KDM5 inhibition Overall design: Since our CRISPR screen identified ZBTB7A as a modulator of C70-sensitivity, we aimed to investigate how ZBTB7A and KDM5A/B interact to regulate H3K4me3 and gene expression. We generated ZBTB7A, KDM5A, and KDM5B knockout cell lines in SM149. As a WT control, cells expressing the ROSA26-targeting gRNA were generated (i.e., ROSA26_KO). The effect of each knockout and treatment (-/+ 10 µM C70 for 7 days) on chromatin binding patterns for ZBTB7A, KDM5A, KDM5B, and H3K4me3 were examined.