Plays a role in hippocampal-dependent synaptic plasticity, learning and memory. Involved in the formation of spines and functional synaptic contacts by modulating the translational activity of the cytoplasmic polyadenylation element-binding protein CPEB3. Promotes ubiquitination of CPEB3, and hence induces CPEB3-dependent mRNA translation activation of glutamate receptor GRIA1 and GRIA2. Can function as an E3 ubiquitin-protein ligase to activate monoubiquitination of JAG1 (in vitro), thereby regulating the Notch pathway. Acts as a tumor suppressor; inhibits malignant cell transformation of medulloblastoma (MB) cells by inhibiting the Notch signaling pathway. S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Interacts with CPEB3 (via N-terminal domain); the interaction increases CPEB3 ubiquitination. Interacts with DLL1. Localized in the cell bodies of the pyramidal neurons and distributed along their apical dendrites. Colocalized with PSD95 in postsynaptic sites. Colocalized with CPEB3 at apical dendrites of CA1 neurons (By similarity). Colocalized with JAG1 at the cell surface. Expressed in brain, testis, pituitary gland, pancreas and bone marrow. Also poorly expressed in malignant astrocytomas and several neuroectodermal tumor cell lines. Weakly expressed in medulloblastoma (MB) compared with normal cerebellar tissues. Down-regulated in medulloblastoma (MB). Myristoylation is a determinant of membrane targeting.