MONOCLONAL ANTIMYOGENIN ANTIBODIES DEFINE EPITOPES OUTSIDE THE BHLH DOMAIN WHERE BINDING INTERFERES WITH PROTEIN-PROTEIN AND PROTEIN-DNA INTERACTIONS

We have developed a panel of monoclonal antibodies against rat myogeni n, a skeletal muscle regulatory protein of the bHLH family. Some of th ese monoclonals have been widely used by others, and details of their production are presented. Mapping the epitopes by immunoprecipitation of myogenin deletion mutants demonstrates that this panel recognizes e pitopes spanning the entire molecule outside the HLH region. Four anti bodies against epitopes outside the bHLH region interfere with the bin ding of myogenin/E-protein heterodimers to DNA sequences containing th e myogenin heterodimer consensus recognition site. Three of these epit opes are partially masked in the heterodimers; antibody binding to the se epitopes reduces the interactions between myogenin and E12. This su ggests that surfaces outside the HLH dimerization domain may contribut e to the stability of myogenin/E12 complexes. The binding of one antib ody to its epitope did not appear to affect the myogenin/E12 interacti on but nonetheless interfered with the binding of the complex to DNA, suggesting that this epitope lies near to a surface occupied by DNA. ( C) 1996 Wiley-Liss, Inc.