Ourpreviousstudiesshowedapredominanceofhighmolecularweightproteingroupintumornuclearmatrices.Contrarytonormalcells,proteinsofthisgrouparepreferentiallyphosphorylated.Phosphoproteinsofhepatomanuclearmatrixareselectivelysubjectedtorapidproteolysis.Byalkalitreatmentandamonoclonalantibodyagainstphosphotyrosylresiduethepresenceoftwohighmolecularweightbandsofphosphotyrosyl-containingproteinswasdetectedinnuclearmatricesoftumorbutnotofnormallivercells.Highmolecularweightproteingroupoftumornuclearmatricesrevealedalsoarapidturnoverandpreferentialincorporationoflabeledaminoacidsselectivelyinhibitedbychloramphenicol.