E3 ubiquitin-protein ligase SIAH1B (Siah1b)

E3 ubiquitin ligases take ubiquitin from an E2 ubiquitin- conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates. Mediates E3 ubiquitin ligase activity either through direct binding to substrates or by working as the essential RING domain subunit of larger E3 complexes.

Confers constitutive instability to HIPK2 through proteasomal degradation. Probably activates the ubiquitin- mediated degradation of many substrates.