The Evolutionary Rates of Eukaryotic RNA Polymerases and of Their Transcription Factors Are Affected by the Level of Concerted Evolution of the Genes They Transcribe

A defining characteristic of all eukaryotes is the presence of three RNA polymerases, each of which transcribes a particular subset of nuclear genes. RNA polymerase I transcribes rRNA genes; RNA polymerase II transcribes mRNA, miRNA, snRNA, and snoRNA genes; and RNA polymerase III transcribes 5S rRNA and tRNA genes. Here, we use the sequences of up to 25 Ascomycete species to show that the type of genes transcribed by each RNA polymerase affects their evolutionary rates and those of their transcription factors (TFs). The RNA polymerase subunits and TFs of genes whose promoters experience higher levels of concerted evolution evolve significantly faster than those experiencing lower levels of concerted evolution. The rates of evolution of RNA polymerase genes and their TFs are therefore not only the result of diverse selective constraints but are also influenced by the level of concerted evolution of the genes they transcribe.