• Open Access

DNA glycosylase encoded by MUTYH functions as a molecular switch for programmed cell death under oxidative stress to suppress tumorigenesis

Authors

  • Sugako Oka,

    1. Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
    Search for more papers by this author
  • Yusaku Nakabeppu

    Corresponding author
    1. Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
      To whom correspondence should be addressed. E-mail: yusaku@bioreg.kyushu-u.ac.jp
    Search for more papers by this author

To whom correspondence should be addressed. E-mail: yusaku@bioreg.kyushu-u.ac.jp

Abstract

8-oxoguanine is a major base lesion in DNA or in nucleotides caused by oxidative stress, and is highly mutagenic because it can pair with adenine as well as cytosine. Adenine DNA glycosylase, encoded by the human mutY homolog gene, MUTYH, excises adenine in the nascent strand when inserted opposite 8-oxoguanine in template DNA, and thus suppresses mutagenesis caused by 8-oxoguanine that has accumulated in DNA due to oxidative stress. Several germ-line mutations in MUTYH are predisposed to MUTYH-associated polyposis, an autosomal recessive disorder characterized by multiple colorectal adenomas and carcinomas. Loss of function of MUTYH leads to an accumulation of somatic mutations in APC and KRAS genes, resulting in the development of adenomas/carcinomas. We recently demonstrated that accumulation of 8-oxoguanine in nuclear and mitochondrial DNA triggers two distinct cell death pathways that are independent of each other. Both pathways are initiated by the accumulation of MUTYH-generated single-strand breaks (SSBs) in nuclear or mitochondrial DNA. Our findings indicate that MUTYH-induced cell death due to oxidative stress results in an efficient elimination of mutagenic cells that have accumulated high levels of 8-oxoguanine in their DNAs. It is most likely that loss of function of MUTYH in stem or progenitor cells in the intestinal epithelium of MUTYH-associated polyposis patients results in escape from programmed cell death; however, accumulated 8-oxoguanine causes various mutations in APC or KRAS genes in these proliferative cells, thereby promoting tumorigenesis. We thus propose that MUTYH suppresses tumorigenesis under conditions of oxidative stress by inducing cell death and by suppressing mutagenesis. (Cancer Sci 2011; 102: 677–682)

Ancillary