The identification of a novel gene, MAPO2, that is involved in the induction of apoptosis triggered by O⁶-methylguanine

PLoS One. 2012;7(9):e44817. doi: 10.1371/journal.pone.0044817. Epub 2012 Sep 24.

Abstract

O⁶-Methylguanine, one of alkylated DNA bases, is especially mutagenic. Cells containing this lesion are eliminated by induction of apoptosis, associated with the function of mismatch repair (MMR) proteins. A retrovirus-mediated gene-trap mutagenesis was used to isolate new genes related to the induction of apoptosis, triggered by the treatment with an alkylating agent, N-methyl-N-nitrosourea (MNU). This report describes the identification of a novel gene, MAPO2 (O⁶-methylguanine-induced apoptosis 2), which is originally annotated as C1orf201. The MAPO2 gene is conserved among a wide variety of multicellular organisms and encodes a protein containing characteristic PxPxxY repeats. To elucidate the function of the gene product in the apoptosis pathway, a human cell line derived from HeLa MR cells, in which the MAPO2 gene was stably knocked down by expressing specific miRNA, was constructed. The knockdown cells grew at the same rate as HeLa MR, thus indicating that MAPO2 played no role in the cellular growth. After exposure to MNU, HeLa MR cells and the knockdown cells underwent cell cycle arrest at G₂/M phase, however, the production of the sub-G₁ population in the knockdown cells was significantly suppressed in comparison to that in HeLa MR cells. Moreover, the activation of BAK and caspase-3, and depolarization of mitochondrial membrane, hallmarks for the induction of apoptosis, were also suppressed in the knockdown cells. These results suggest that the MAPO2 gene product might positively contribute to the induction of apoptosis triggered by O⁶-methylguanine.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Animals
  • Apoptosis / drug effects*
  • Apoptosis / genetics*
  • Apoptosis Regulatory Proteins / chemistry
  • Apoptosis Regulatory Proteins / deficiency
  • Apoptosis Regulatory Proteins / genetics*
  • Apoptosis Regulatory Proteins / metabolism
  • G2 Phase Cell Cycle Checkpoints / drug effects
  • G2 Phase Cell Cycle Checkpoints / genetics
  • Gene Knockdown Techniques
  • Guanine / analogs & derivatives*
  • Guanine / pharmacology
  • HeLa Cells
  • Humans
  • M Phase Cell Cycle Checkpoints / drug effects
  • M Phase Cell Cycle Checkpoints / genetics
  • Methylnitrosourea / pharmacology
  • Mice
  • Molecular Sequence Data
  • Rats

Substances

  • Apoptosis Regulatory Proteins
  • MAPO2 protein, human
  • MAPO2 protein, mouse
  • Guanine
  • Methylnitrosourea
  • O-(6)-methylguanine

Grants and funding

This work was supported by the Cancer Research Fund from Fukuoka Foundation for Sound Health (to RF), MEXT-Grants-in-Aid and MEXT-Supported Program for the Strategic Research Foundation at Private Universities, 2008–2012. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.