Update information. We established an APEX proximity labeling strategy in coupled with mass spectrometry to identify interacting proteins of RNF214. In this approach, we first fused an engineered ascorbate peroxidase (APEX2) to either N-terminus or C-terminus of RNF214, expressed these two fusion proteins in HLF, an HCC cell line, near the endogenous level, and generated short-lived radicals around the APEX2-RNF214 fusion proteins to label biotin on nearby interactive proteins by adding hydrogen peroxide (H2O2) and biotin-phenol (also called biotin-tyramide) transiently. Biotinylated proteins were then isolated using Streptavidin resin for protein identification by mass spectrometry.