E3 ubiquitin-protein ligase which accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates. Ubiquitinates ERBB4 isoforms JM-A CYT-1 and JM-B CYT-1, KLF2, KLF5 and TP63 and promotes their proteasomal degradation. Ubiquitinates RNF11 without targeting it for degradation. Ubiquitinates and promotes degradation of TGFBR1; the ubiquitination is enhanced by SMAD7. Ubiquitinates SMAD6 and SMAD7. Ubiquitinates and promotes degradation of SMAD2 in response to TGF-beta signaling, which requires interaction with TGIF. Activates the Hippo signaling pathway in response to cell contact inhibition and recruitment to the Crumbs complex at the cell membrane (PubMed:34404733). Monoubiquitinates AMOTL2 which facilitates its interaction with and activation of LATS2 (PubMed:34404733). LATS2 then phosphorylates YAP1, excluding it from the nucleus and therefore ultimately represses YAP1-driven transcription of target genes (PubMed:34404733). {ECO:0000269|PubMed:12535537, ECO:0000269|PubMed:15221015, ECO:0000269|PubMed:15359284, ECO:0000269|PubMed:34404733}. This is the function of ENSG00000123124 (WWP1, WW domain containing E3 ubiquitin protein ligase 1).