PA2G4 may play a role in a ERBB3-regulated signal transduction pathway and seems be involved in growth regulation. This protein acts a corepressor of the androgen receptor (AR) and is regulated by the ERBB3 ligand neuregulin-1/heregulin (HRG). Also, this protein Inhibits transcription of some E2F1-regulated promoters, probably by recruiting histone acetylase (HAT) activity, and binds RNA. The protein is associated with 28S, 18S and 5.8S mature rRNAs, several rRNA precursors and probably U3 small nucleolar RNA, that may be involved in regulation of intermediate and late steps of rRNA processing, and may be involved in ribosome assembly. The protein mediates cap-independent translation of specific viral IRESs (internal ribosomal entry site) (By similarity), and regulates cell proliferation, differentiation, and survival. Isoform 1 suppresses apoptosis whereas isoform 2 promotes cell differentiation (By similarity).