 The modification is thought to increase the stability of mRNA during heat shock before the RNA goes to the nucleus or mitochondria, but more studies are needed.The RluA domain of these proteins can identify the substrate through a different protein binding to the substrate and then particular bonds to the RluA domain.PUS 5 is not well studied and located pseudouridine synthase and similar to Pus 2 does not have a mitochondrial signal targeting sequence.