E3 ubiquitin ligase that ubiquitinates APBB1 for its degradation by the proteasome and thus prevents apoptosis and promotes survival of neurons (By similarity). Has a dual role in neurons as it is also required for dendrite growth and maintenance for which its ligase activity is not critical (By similarity). May act as a scaffold molecule to regulate this process (By similarity). Acts as a downstream effector of the interconnected PI3K and MAPK signaling pathways and thus participates in the regulation of the cell cycle (By similarity). 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. Interacts with APBB1 (By similarity). Interacts with CHD1; CHD1-binding controls RNF157 stability (By similarity). Interacts also with ATRN, MEGF8, TECR, MSI2, PLRG1, BYSL, MTERF3, PSMA1, MRPS18B, PRPF4, FASTKD2, SLC25A1, SMU1, CNOT9, MRPS2, MAGT1, FXR2, EMD, PSMD8, HDAC1, RAN, HSD17B12, TXNDC5 AND MRPL19 (By similarity). Predominantly expressed in the brain (PubMed:25342469). The D-box motifs play a key role in RNF157 stabilization.