Myc-epitope tagged proteins detected with the 9E10 antibody in immunofluorescence and immunoprecipitation assays but not in Western blot analysis

A human Myc epitope is frequently used to tag proteins for expression experiments in nonhuman cells. We used the monoclonal 9E10 antibody specific for this epitope to analyse the expression of four proteins carrying the Myc tag in cells transfected with expression vectors. While all four proteins can be detected by immunofluorescence and immunoprecipitation assays, surprisingly, only two proteins could be detected in Western blot analysis, indicating that epitope recognition by the monoclonal antibody can be blocked in some membrane-retained ectopic proteins. Other techniques such as immunofluorescence and immunoprecipitation assays can be successfully used with the 9E10 antibody to determine potential expression of Myc-tagged proteins.