Lesion bypass activity of DNA polymerase θ (POLQ) is an intrinsic property of the pol domain and depends on unique sequence inserts.
DNA polymerase θ (POLQ, polθ) is a large, multidomain DNA polymerase encoded in higher eukaryotic genomes. It is important for maintaining genetic stability in cells and helping protect cells from DNA damage caused by ionizing radiation. POLQ contains an N-terminal helicase-like domain, a large central domain of indeterminate function, and a C-terminal polymerase domain with sequence similarity to the A-family of DNA polymerases. The enzyme has several unique properties, including low fidelity and the ability to insert and extend past abasic sites and thymine glycol lesions. It is not known whether the abasic site bypass activity is an intrinsic property of the polymerase domain or whether helicase activity is also required. Three "insertion" sequence elements present in POLQ are not found in any other A-family DNA polymerase, and it has been proposed that they may lend some unique properties to POLQ. Here, we analyzed the activity of the DNA polymerase in the absence of each sequence insertion. We found that the pol domain is capable of highly efficient bypass of abasic sites in the absence of the helicase-like or central domains. Insertion 1 increases the processivity of the polymerase but has little, if any, bearing on the translesion synthesis properties of the enzyme. However, removal of insertions 2 and 3 reduces activity on undamaged DNA and completely abrogates the ability of the enzyme to bypass abasic sites or thymine glycol lesions.
Department of Microbiology and Molecular Genetics, University of Vermont, 95 Carrigan Drive, Burlington, VT 05405, USA.
Matthew
M
Hogg
Mineaki
M
Seki
Richard D
RD
Wood
Sylvie
S
Doublié
Susan S
SS
Wallace
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry* / Q000235:genetics; D015751:Genes, pol; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D013941:Thymine / Q000031:analogs & derivatives / Q000737:chemistry; D000097462:DNA Polymerase theta
D004259:DNA-Directed DNA Polymerase; D013941:Thymine; D000097462:DNA Polymerase theta; C029389:thymine glycol