A class of GATA3 mutation reprograms the breast cancer transcriptional network through gain and loss of function

A pioneer transcription factor, GATA3, is one of the most frequently mutated genes in breast cancer, yet the impact of these mutations is largely unknown. We generated a GATA3 mutant cell line (T47D wt/R330fs) by CRISPR. Mutation of one allele of GATA3 led to loss of binding and decreased expression at a subset of genes, including Progesterone Receptor. At other loci, associated with epithelial to mesenchymal transition, gain of binding at a novel sequence motif correlated with increased gene expression. Our results illuminate tumor-promoting functions of specific GATA3 mutations in breast cancer. Overall design: Genome-wide mapping of chromatin localization of luminal transcription factors in GATA3 mutant cells