Folate deficiency in vitro induces uracil misincorporation and DNA hypomethylation and inhibits DNA excision repair in immortalized normal human colon epithelial cells

Susan Joyce Duthie, S Narayanan, S Blum, Lynn Peters Pirie, G M Brand

Research output: Contribution to journalArticlepeer-review

185 Citations (Scopus)

Abstract

Epidemiological studies have indicated that folic acid protects against a variety of cancers, particularly cancer of the colorectum. Folate is essential for efficient DNA synthesis and repair. Moreover folate can affect cellular S-adenosylmethionine levels, which regulate DNA methylation and control gene expression. We have investigated the mechanisms through which folate affects DNA stability in immortalized normal human colonocytes (HCEC). DNA strand breakage, uracil misincorporation, and DNA repair, in response to oxidative and alkylation damage, were determined in folate-sufficient and folate-deficient colonocytes by single cell gel electrophoresis. In addition, methyl incorporation into genomic DNA was measured using the bacterial enzyme Sss1 methylase. Cultured human colonocyte DNA contained endogenous strand breaks and uracil. Folate deficiency significantly increased strand breakage and uracil misincorporation in these cells. This negative effect on DNA stability was concentration dependent at levels usually found in human plasma (1-10 ng/ml). DNA methylation was decreased in HCEC grown in the absence of folate. Conversely, hypomethylation was nor concentration dependent. Folate deficiency impaired the ability of HCEC to repair oxidative and alkylation damage. These results demonstrate that folic acid modulates DNA repair DNA strand breakage, and uracil misincorporation in immortalized human colonocytes and that folate deficiency substantially decreases DNA stability in these cells.

Original languageEnglish
Pages (from-to)245-251
Number of pages7
JournalNutrition and Cancer
Volume37
Issue number2
DOIs
Publication statusPublished - 2000

Keywords

  • HAMSTER OVARY CELLS
  • COLORECTAL-CANCER RISK
  • IN-VITRO
  • ULCERATIVE-COLITIS
  • ALKYLATING-AGENTS
  • DAMAGE
  • LINE
  • EXPRESSION
  • METABOLISM
  • CARCINOMA

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