EBP1 (ErbB-3-binding protein 1), also known as PA2G4 (proliferation-associated 2G4), p38-2G4 or HG4-1, is a member of the peptidase M24C family and functions as an RNA-binding protein involved in cellular proliferation and differentiation processes. It is expressed in a variety of cell lines, including a wide range of tumor cell lines, and localizes to the cytoplasm. Upon treatment with Neuregulin-1 (heregulin), EBP1 translocates to the nucleus. EBP1 is a component of pre-ribosomal ribonucleoprotein complexes, participating in ribosome assembly and regulating the later steps of rRNA processing. In addition, EBP1 interacts with ErbB-3 and may function as a modulator of the ErbB-3-mediated signal transduction pathway by regulating the effects of Neuregulin-1. EBP1 also associates with histone deacetylases (HDACs), functioning as a transcriptional corepressor of cell cycle regulatory genes.