CRISPR–Cas screening for enhancers

Korkmaz et al. describe a CRISPR–Cas9-based screening method for the functional analysis of endogenous enhancers. The method is based on bioinformatics analyses to delineate sets of potential enhancers of interest, followed by cloning of single guide RNA (sgRNA) libraries to target the enhancers by CRISPR–Cas9 and screening for enhancers that are active in specific cellular settings. Using this method, the authors discovered a new p53-bound enhancer (p53^enh3507) of the p53 effector gene CDKN1A, which is required for p53-dependent, oncogene-induced senescence (OIS) in immortalized human cells, as well as a new CCND1 enhancer that mediates ERα-dependent breast cancer cell proliferation. Additionally, the use of CRISPR–Cas9 with sgRNAs tiling the 2 kb region surrounding p53^enh3507 enabled pinpointing new domains that are not bound by p53 but that are nevertheless required for p53-dependent OIS.