Abstract
The APOBEC3 family of cytosine deaminases, which target single-stranded DNA and RNA of viruses and retroelements as part of the innate immune defense, generate mutations in many human cancers. Although the APOBEC3A paralog is a major endogenous source of these mutations, low APOBEC3A mRNA levels and protein abundance have hampered functional characterization. Extensive homology across APOBEC3 paralogs have further challenged the development of specific detection reagents. Here, we describe the isolation and use of monoclonal antibodies with specificity for APOBEC3A and the APOBEC3A/APOBEC3B/APOBEC3G proteins. We provide protocols and technical advice for detection and measurement of APOBEC3A protein across human cancer cell lines using standard immunoblotting and immunofluorescence protocols.