E3 ubiquitin ligase that ubiquitinates APBB1 for its degradation by the proteasome and thus prevents apoptosis and promotes survival of neurons (PubMed:25342469). Has a dual role in neurons as it is also required for dendrite growth and maintenance for which its ligase activity is not critical (PubMed:25342469). May act as a scaffold molecule to regulate this process (PubMed:25342469). Acts as a downstream effector of the interconnected PI3K and MAPK signaling pathways and thus participates in the regulation of the cell cycle (PubMed:28655764). 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 (PubMed:25342469). Interacts with CHD1; CHD1-binding controls RNF157 stability (PubMed:28655764). Interacts 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 (PubMed:28655764). Expression is cell cycle-specific with higher levels in cells arrested in G1/S and G2/M (PubMed:28655764). The D-box motifs play a key role in RNF157 stabilization (PubMed:28655764). Phosphorylation at Ser-660, Ser-661, Ser-662 and Ser-663 downstream of the PI3K and MAPK pathways influences the E3 ligase activity and stability of RNF157 during the cell cycle in an anaphase-promoting complex/cyclosome-CDH1-dependent manner (PubMed:28655764).