poliota, a remarkably error-prone human DNA polymerase.
The Saccharomyces cerevisiae RAD30 gene encodes DNA polymerase eta. Humans possess two Rad30 homologs. One (RAD30A/POLH) has previously been characterized and shown to be defective in humans with the Xeroderma pigmentosum variant phenotype. Here, we report experiments demonstrating that the second human homolog (RAD30B), also encodes a novel DNA polymerase that we designate poliota. poliota, is a distributive enzyme that is highly error-prone when replicating undamaged DNA. At template G or C, the average error frequency was approximately 1 x 10(-2). Our studies revealed, however, a striking asymmetry in misincorporation frequency at template A and T. For example, template A was replicated with the greatest accuracy, with misincorporation of G, A, or C occurring with a frequency of approximately 1 x 10(-4) to 2 x 10(-4). In dramatic contrast, most errors occurred at template T, where the misincorporation of G was, in fact, favored approximately 3:1 over the correct nucleotide, A, and misincorporation of T occurred at a frequency of approximately 6.7 x 10(-1). These findings demonstrate that poliota is one of the most error-prone eukaryotic polymerases reported to date and exhibits an unusual misincorporation spectrum in vitro.
Tissier
A
A
Section on DNA Replication, Repair, and Mutagenesis, National Institute of Child Health and Human Development, Bethesda, MD 20892-2725, USA.
McDonald
J P
JP
Frank
E G
EG
Woodgate
R
R
D001483:Base Sequence; D017931:DNA Primers; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D009154:Mutation
D017931:DNA Primers; D007527:Isoenzymes; D004259:DNA-Directed DNA Polymerase