Roles of common subunits within distinctmultisubunit complexes

Abstract

Currently, there is no method to distinguish between the roles ofa subunit in one multisubunit protein complex from its roles inother complexes in vivo. This is because a mutation in a commonsubunit will affect all complexes containing that subunit. Here, wedescribe a unique method to discriminate between the functionsof a common subunit in different multisubunit protein complexes.In this method, a common subunit in a multisubunit protein complex is genetically fused to a subunit that is specific to that complex and point mutated. The resulting phenotype(s) identify thespecific function(s) of the subunit in that complex only. HistoneH2B is a common subunit in nucleosomes containing H2A/H2B orHtz1/H2B dimers. The H2B was fused to H2A or Htz1 and pointmutated. This strategy revealed that H2B has common and distinctfunctions in different nucleosomes. This method could be used tostudy common subunits in other multisubunit protein complexes.