TI  - Analysis of the oligomerization of <prot>myogenin</prot> and <prot>E2A</prot> products in vivo using
      a two-hybrid assay system.
PG  - 17498-501
AB  - Members of the helix-loop-helix (HLH) family of proteins bind DNA and
      activate transcription as homo- and heterodimers.    <prot>Myogenin</prot>    is a
      muscle-specific HLH protein that binds DNA in vitro as a heterodimer with
      several widely expressed HLH proteins, such as the  <prot>E2A</prot>  gene products  <prot>E12</prot> 
      and  <prot>E47</prot> . We describe a method for detection of protein-protein
      interactions among HLH proteins in vivo in which dimerization through the
      HLH motif reconstructs a hybrid transcription factor containing the
      DNA-binding domain of yeast GAL4 linked to one HLH motif and the
      activation domain of <prot>VP-16</prot> linked to another. We have used this assay to
      investiagate whether myogenin forms homomeric or heteromeric complexes in
      vivo and to determine whether growth factors and oncogenes that inhibit
      myogenesis influence myogenin's ability to dimerize. The results show that
        <prot>myogenin</prot>   heterodimerizes with  <prot>E12</prot>  and  <prot>E47</prot>  in vivo, but it does not
      homodimerize to a measurable extent. Peptide growth factors, as well as
      the immediate early gene products <prot>c-Jun</prot>, <prot>v-Fos</prot>, and <prot>c-Myc</prot>, inhibit the
      activity of myogenin through a mechanism independent of its association
      with <prot>E2A</prot> products.
AD  - Department of Biochemistry and Molecular Biology, University of Texas M.
