We show that yeast protein Yel055cp, which has been identified as the fifth essential DNA polymerase in Saccharomyces cerevisiae (POL5), is a member of a family of predicted rDNA transcription regulators (typified by human MYB-binding protein MYBBP1 A), which are represented by a single ortholog in all animals, fungi and plants with sequenced genomes. These proteins are confidently predicted to have an entirely a-helical structure and are unrelated to the B class DNA polymerases, as claimed for yeast POL5, or any other known polymerases.