Characterization of a natural mutator variant of human DNA polymerase lambda which promotes chromosomal instability by compromising NHEJ.
BACKGROUND
DNA polymerase lambda (Pollambda) is a DNA repair polymerase, which likely plays a role in base excision repair (BER) and in non-homologous end joining (NHEJ) of DNA double-strand breaks (DSB).


RESULTS
Here, we described a novel natural allelic variant of human Pollambda (hPollambda) characterized by a single nucleotide polymorphism (SNP), C/T variation in the first base of codon 438, resulting in the amino acid change Arg to Trp. In vitro enzyme activity assays of the purified W438 Pollambda variant revealed that it retained both DNA polymerization and deoxyribose phosphate (dRP) lyase activities, but had reduced base substitution fidelity. Ectopic expression of the W438 hPollambda variant in mammalian cells increases mutation frequency, affects the DSB repair NHEJ pathway, and generates chromosome aberrations. All these phenotypes are dependent upon the catalytic activity of the W438 hPollambda.


CONCLUSIONS
The expression of a cancer-related natural variant of one specialized DNA polymerase can be associated to generic instability at the cromosomal level, probably due a defective NHEJ. These results establish that chromosomal aberrations can result from mutations in specialized DNA repair polymerases.
Terrados
Gloria
G
Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain.
Capp
Jean-Pascal
JP
Canitrot
Yvan
Y
García-Díaz
Miguel
M
Bebenek
Katarzyna
K
Kirchhoff
Tomas
T
Villanueva
Alberto
A
Boudsocq
François
F
Bergoglio
Valérie
V
Cazaux
Christophe
C
Kunkel
Thomas A
TA
Hoffmann
Jean-Sébastien
JS
Blanco
Luis
L
D000596:Amino Acids / Q000737:chemistry; D001120:Arginine / Q000737:chemistry; D043171:Chromosomal Instability / Q000235:genetics*; D002869:Chromosome Aberrations; D003062:Codon; D004247:DNA / Q000737:chemistry; D053903:DNA Breaks, Double-Stranded; D004252:DNA Mutational Analysis; D019951:DNA Polymerase beta / Q000235:genetics* / Q000502:physiology; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D009154:Mutation; D020641:Polymorphism, Single Nucleotide; D014364:Tryptophan / Q000737:chemistry
D000596:Amino Acids; D003062:Codon; D004268:DNA-Binding Proteins; C508551:NHEJ1 protein, human; D014364:Tryptophan; D004247:DNA; D001120:Arginine; C415367:DNA polymerase beta2; D019951:DNA Polymerase beta; D045643:DNA Repair Enzymes