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Modulation of DNA polymerase beta-dependent base excision repair in cultured human cells after low dose exposure to arsenite

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posted on 2023-05-16, 20:57 authored by Sykora, P, Elizabeth Snow
Base excision repair (BER) is crucial for development and for the repair of endogenous DNA damage. However, unlike nucleotide excision repair, the regulation of BER is not well understood. Arsenic, a well-established human carcinogen, is known to produce oxidative DNA damage, which is repaired primarily by BER, whilst high doses of arsenic can also inhibit DNA repair. However, the mechanism of repair inhibition by arsenic and the steps inhibited are not well defined. To address this question we have investigated the regulation of DNA polymerase β (Pol β) and AP endonuclease (APE1), in response to low, physiologically relevant doses of arsenic. GM847 lung fibroblasts and HaCaT keratinocytes were exposed to sodium arsenite, As(III), and mRNA, protein levels and BER activity were assessed. Both Pol β and APE1 mRNA exhibited significant dose-dependant down regulation at doses of As(III) above 1 μM. However, at lower doses Pol β mRNA and protein levels, and consequently, BER activity were significantly increased. In contrast, APE1 protein levels were only marginally increased by low doses of As(III) and there was no correlation between APE1 and overall BER activity. Enzyme supplementation of nuclear extracts confirmed that Pol β was rate limiting. These changes in BER correlated with overall protection against sunlight UV-induced toxicity at low doses of As(III) and produced synergistic toxicity at high doses. The results provide evidence that changes in BER due to low doses of arsenic could contribute to a non-linear, threshold dose response for arsenic carcinogenesis. © 2008 Elsevier Inc. All rights reserved.

History

Publication title

Toxicology and Applied Pharmacology

Volume

228

Pagination

385-394

ISSN

0041-008X

Department/School

School of Health Sciences

Publisher

Academic Press Inc Elsevier Science

Place of publication

San Diego, Ca 92101-4495 USA,

Repository Status

  • Restricted

Socio-economic Objectives

Clinical health not elsewhere classified

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