Kim J, Song I, Jo A, Shin JH, Cho H, Eoff RL, Guengerich FP, Choi JY. Biochemical analysis of six genetic variants of error-prone human DNA polymerase ι involved in translesion DNA synthesis.
Chem Res Toxicol 2014;
27:1837-52. [PMID:
25162224 PMCID:
PMC4203391 DOI:
10.1021/tx5002755]
[Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
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DNA
polymerase (pol) ι is the most error-prone among the
Y-family polymerases that participate in translesion synthesis (TLS).
Pol ι can bypass various DNA lesions, e.g., N2-ethyl(Et)G, O6-methyl(Me)G,
8-oxo-7,8-dihydroguanine (8-oxoG), and an abasic site, though frequently
with low fidelity. We assessed the biochemical effects of six reported
genetic variations of human pol ι on its TLS properties, using
the recombinant pol ι (residues 1–445) proteins and DNA
templates containing a G, N2-EtG, O6-MeG, 8-oxoG, or abasic site. The Δ1–25
variant, which is the N-terminal truncation of 25
residues resulting from an initiation codon variant (c.3G > A)
and
also is the formerly misassigned wild-type, exhibited considerably
higher polymerase activity than wild-type with Mg2+ (but
not with Mn2+), coinciding with its steady-state kinetic
data showing a ∼10-fold increase in kcat/Km for nucleotide incorporation
opposite templates (only with Mg2+). The R96G variant,
which lacks a R96 residue known to interact with the incoming nucleotide,
lost much of its polymerase activity, consistent with the kinetic
data displaying 5- to 72-fold decreases in kcat/Km for nucleotide incorporation
opposite templates either with Mg2+ or Mn2+,
except for that opposite N2-EtG with Mn2+ (showing a 9-fold increase for dCTP incorporation). The
Δ1–25 variant bound DNA 20- to 29-fold more tightly than
wild-type (with Mg2+), but the R96G variant bound DNA 2-fold
less tightly than wild-type. The DNA-binding affinity of wild-type,
but not of the Δ1–25 variant, was ∼7-fold stronger
with 0.15 mM Mn2+ than with Mg2+. The results
indicate that the R96G variation severely impairs most of the Mg2+- and Mn2+-dependent TLS abilities of pol ι,
whereas the Δ1–25 variation selectively and substantially
enhances the Mg2+-dependent TLS capability of pol ι,
emphasizing the potential translational importance of these pol ι
genetic variations, e.g., individual differences in TLS, mutation,
and cancer susceptibility to genotoxic carcinogens.
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