Protein interaction map of APOBEC3 enzyme family

Human APOBEC3 enzymes are a family of single-stranded (ss)DNA and RNA cytidine deaminases that act as part of the intrinsic immunity against viruses and retroelements. APOBEC3s deaminate cytosine to form uracil which can functionally inactivate or cause degradation of viral or retroelement genomes. In addition, APOBEC3 proteins have deamination independent anti-viral activity and aberrant regulation of APOBEC3 expression can result in the deamination and mutagenesis of the genome contributing to cancer initiation and evolution. To further understand their cellular roles, we used affinity purification mass spectrometry (AP-MS) to determine the protein-protein interaction (PPI) network for the human APOBEC3 enzymes and uncovered a diverse number of protein-protein and protein-RNA mediated interactions. PPIs with the Prefoldin family of protein folding chaperones were identified for APOBEC3B, APOBEC3D, and APOBEC3F. The APOBEC3B and prefoldin 5 (PFD5) interaction disrupted the ability of PFD5 to induce degradation of the oncogene cMyc, implicating a deamination independent contribution of APOBEC3B to cancer. Altogether, the results uncover novel functions and interactions of the APOBEC3 family and suggest that they may have fundamental roles in cellular RNA biology, their roles are not redundant, and there is a deamination independent influence on cancer.