RNA Polymerase I Transcription Factor Rrn3 Is Functionally Conserved between Yeast and Human

We have cloned a human cDNA that is related to the RNA polymerase I transcription factor Rrn3 of Saccharomyces cerevisiae. The recombinant human protein displays both sequence similarity and immunological crossreactivity to yeast Rrn3 and is capable of rescuing a yeast strain carrying a disruption of the RRN3 gene in vivo. Point mutation of an amino acid that is conserved between the yeast and human proteins compromises the function of each factor, confirming that the observed sequence similarity is functionally significant. Rrn3 is the first RNA polymerase I-specific transcription factor shown to be functionally conserved between yeast and mammals, suggesting that at least one mechanism that regulates ribosomal RNA synthesis is conserved among eukaryotes.