PELP1 is a reader of histone H3 methylation that facilitates oestrogen receptor-α target gene activation by regulating lysine demethylase 1 specificity

Histone methylation has a key role in oestrogen receptor (ERα)-mediated transactivation of genes. Proline glutamic acid and leucine-rich protein 1 (PELP1) is a new proto-oncogene that functions as an ERα co-regulator. In this study, we identified histone lysine demethylase, KDM1, as a new PELP1-interacting protein. These proteins, PELP1 and KDM1, were both recruited to ERα target genes, and PELP1 depletion affected the dimethyl histone modifications at ERα target genes. Dimethyl-modified histones H3K4 and H3K9 are recognized by PELP1, and PELP1 alters the substrate specificity of KDM1 from H3K4 to H3K9. Effective demethylation of dimethyl H3K9 by KDM1 requires a KDM1-ERα-PELP1 functional complex. These results suggest that PELP1 is a reader of H3 methylation marks and has a crucial role in modulating the histone code at the ERα target genes.