Human DNA polymerase N (POLN) is a low fidelity enzyme capable of error-free bypass of 5S-thymine glycol.
Human DNA polymerase N (POLN or pol nu) is the most recently discovered nuclear DNA polymerase in the human genome. It is an A-family DNA polymerase related to Escherichia coli pol I, human POLQ, and Drosophila Mus308. We report the first purification of the recombinant enzyme and examination of its biochemical properties, as a step toward understanding the functions of POLN. Unusual for an A-family DNA polymerase, POLN is a low fidelity enzyme incorporating T opposite template G with a frequency of 0.45 and G opposite template T with a frequency of 0.021. The frequency of misincorporation of T opposite template G is higher than any other known DNA polymerase. POLN has a processivity of DNA synthesis (1-100 nucleotides) similar to the exonuclease-deficient Klenow fragment of E. coli pol I, is inhibited by dideoxynucleotides, and resistant to aphidicolin. The strand displacement activity of POLN was higher than exonuclease-deficient Klenow fragment. Furthermore, POLN can perform translesion synthesis past thymine glycol, a common endogenous and radiation-induced product of reactive oxygen species damage to DNA. Thymine glycol blocks DNA synthesis by most DNA polymerases, but POLN was particularly adept at efficient and accurate translesion synthesis past a 5S-thymine glycol.
Takata
Kei-ichi
K
Department of Pharmacology, Hillman Cancer Center, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania 15213-1863, USA.
Shimizu
Tatsuhiko
T
Iwai
Shigenori
S
Wood
Richard D
RD
D000595:Amino Acid Sequence; D004249:DNA Damage; D004256:DNA Polymerase I / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry; D006801:Humans; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D013698:Templates, Genetic; D013941:Thymine / Q000031:analogs & derivatives* / Q000737:chemistry; D000097462:DNA Polymerase theta
D004256:DNA Polymerase I; D004259:DNA-Directed DNA Polymerase; D011994:Recombinant Proteins; D013941:Thymine; D000097462:DNA Polymerase theta; C029389:thymine glycol