Polymerase with a protein template

The Rev1 DNA polymerase has forsaken Watson and Crick. Instead of a complementary base, this polymerase uses a protein template, according to Deepak Nair, Aneel Aggarwal (Mount Sinai School of Medicine, New York, NY), and colleagues.

The findings, says Aggarwal, “explain the two mysteries of this polymerase: why it works so well with template G, and why it only puts C opposite it.” The group determined the crystal structure of yeast Rev1 in complex with template DNA and its favorite incoming nucleotide, dCTP. They found several features that distinguish Rev1 from standard eukaryotic polymerases.

First, Rev1 is its own template. An arginine residue within Rev1 acts like a surrogate template G by forming hydrogen bonds with the incoming C. Any other base results in steric hindrance and...