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MUTYH, an adenine DNA glycosylase, mediates p53 tumor suppression via PARP-dependent cell death.

Oka S, Leon J, Tsuchimoto D, Sakumi K, Nakabeppu Y - Oncogenesis (2014)

Bottom Line: We previously reported that 8-oxoguanine (8-oxoG) accumulation in nuclear DNA (nDNA) and mitochondrial DNA triggers two distinct caspase-independent cell death through buildup of single-strand DNA breaks by MutY homolog (MUTYH), an adenine DNA glycosylase.One pathway depends on poly-ADP-ribose polymerase (PARP) and the other depends on calpains.Deficiency of MUTYH causes MUTYH-associated familial adenomatous polyposis.

View Article: PubMed Central - PubMed

Affiliation: 1] Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan [2] Research Center for Nucleotide Pool, Kyushu University, Fukuoka, Japan.

ABSTRACT
p53-regulated caspase-independent cell death has been implicated in suppression of tumorigenesis, however, the regulating mechanisms are poorly understood. We previously reported that 8-oxoguanine (8-oxoG) accumulation in nuclear DNA (nDNA) and mitochondrial DNA triggers two distinct caspase-independent cell death through buildup of single-strand DNA breaks by MutY homolog (MUTYH), an adenine DNA glycosylase. One pathway depends on poly-ADP-ribose polymerase (PARP) and the other depends on calpains. Deficiency of MUTYH causes MUTYH-associated familial adenomatous polyposis. MUTYH thereby suppresses tumorigenesis not only by avoiding mutagenesis, but also by inducing cell death. Here, we identified the functional p53-binding site in the human MUTYH gene and demonstrated that MUTYH is transcriptionally regulated by p53, especially in the p53/DNA mismatch repair enzyme, MLH1-proficient colorectal cancer-derived HCT116+Chr3 cells. MUTYH-small interfering RNA, an inhibitor for p53 or PARP suppressed cell death without an additive effect, thus revealing that MUTYH is a potential mediator of p53 tumor suppression, which is known to be upregulated by MLH1. Moreover, we found that the p53-proficient, mismatch repair protein, MLH1-proficient colorectal cancer cell line express substantial levels of MUTYH in nuclei but not in mitochondria, suggesting that 8-oxoG accumulation in nDNA triggers MLH1/PARP-dependent cell death. These results provide new insights on the molecular mechanism of tumorigenesis and potential new strategies for cancer therapies.

No MeSH data available.


Related in: MedlinePlus

MUTYH mediates p53 tumor suppression via PARP/MLH1-dependent cell death. p53 deficiency leads to MUTYH dysfunction in stem or progenitor cells, which results in escape from programmed cell death under oxidative stress. Accumulated 8-oxoG causes various mutations in tumor-suppressor genes or proto-oncogenes, thereby promoting tumorigenesis. Loss of the mitochondrial form MUTYH in p53-proficient cells also induces carcinogenesis via escape from cell death.
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fig7: MUTYH mediates p53 tumor suppression via PARP/MLH1-dependent cell death. p53 deficiency leads to MUTYH dysfunction in stem or progenitor cells, which results in escape from programmed cell death under oxidative stress. Accumulated 8-oxoG causes various mutations in tumor-suppressor genes or proto-oncogenes, thereby promoting tumorigenesis. Loss of the mitochondrial form MUTYH in p53-proficient cells also induces carcinogenesis via escape from cell death.

Mentions: In this study, we found that the PARP inhibitor, but not the calpain inhibitor, suppresses H2O2-induced cell death in p53-proficient human colorectal cancer cells. PARP is a molecular nick sensor that binds specifically to SSBs, and its specific activity involves catalyzing poly-ADP ribosylation of cellular proteins or of PARP itself and increasing its enzymatic activity by approximately 500-fold.32 In addition, apoptosis-inducing factor translocates to the nucleus in a PARP-dependent manner, and apoptosis-inducing factor/EndoG-mediated nDNA fragmentation represents a major mechanism of caspase-independent apoptosis.33,34 Our data suggest that the PARP-dependent cell death pathway induced by 8-oxoG accumulation in nDNA is mainly activated in the p53-proficient colon cancer cell line under oxidative stress conditions. As shown in Figures 5b and 6b, MUTYH knockdown rescued 10–20% of cells, and this could be equivalent to the population of S-phase cells that can generate SSBs through base excision repair initiated by the nuclear form of MUTYH. In contrast, the calpain inhibitor did not suppress cell death and the mitochondrial form of the MUTYH protein was not detected, suggesting that defects in the cell death pathway induced by 8-oxoG accumulation in mtDNA contribute to decreased sensitivity to oxidative stress, resulting in tumorigenesis or survival of cancer cells (Figure 7).


MUTYH, an adenine DNA glycosylase, mediates p53 tumor suppression via PARP-dependent cell death.

Oka S, Leon J, Tsuchimoto D, Sakumi K, Nakabeppu Y - Oncogenesis (2014)

MUTYH mediates p53 tumor suppression via PARP/MLH1-dependent cell death. p53 deficiency leads to MUTYH dysfunction in stem or progenitor cells, which results in escape from programmed cell death under oxidative stress. Accumulated 8-oxoG causes various mutations in tumor-suppressor genes or proto-oncogenes, thereby promoting tumorigenesis. Loss of the mitochondrial form MUTYH in p53-proficient cells also induces carcinogenesis via escape from cell death.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4216901&req=5

fig7: MUTYH mediates p53 tumor suppression via PARP/MLH1-dependent cell death. p53 deficiency leads to MUTYH dysfunction in stem or progenitor cells, which results in escape from programmed cell death under oxidative stress. Accumulated 8-oxoG causes various mutations in tumor-suppressor genes or proto-oncogenes, thereby promoting tumorigenesis. Loss of the mitochondrial form MUTYH in p53-proficient cells also induces carcinogenesis via escape from cell death.
Mentions: In this study, we found that the PARP inhibitor, but not the calpain inhibitor, suppresses H2O2-induced cell death in p53-proficient human colorectal cancer cells. PARP is a molecular nick sensor that binds specifically to SSBs, and its specific activity involves catalyzing poly-ADP ribosylation of cellular proteins or of PARP itself and increasing its enzymatic activity by approximately 500-fold.32 In addition, apoptosis-inducing factor translocates to the nucleus in a PARP-dependent manner, and apoptosis-inducing factor/EndoG-mediated nDNA fragmentation represents a major mechanism of caspase-independent apoptosis.33,34 Our data suggest that the PARP-dependent cell death pathway induced by 8-oxoG accumulation in nDNA is mainly activated in the p53-proficient colon cancer cell line under oxidative stress conditions. As shown in Figures 5b and 6b, MUTYH knockdown rescued 10–20% of cells, and this could be equivalent to the population of S-phase cells that can generate SSBs through base excision repair initiated by the nuclear form of MUTYH. In contrast, the calpain inhibitor did not suppress cell death and the mitochondrial form of the MUTYH protein was not detected, suggesting that defects in the cell death pathway induced by 8-oxoG accumulation in mtDNA contribute to decreased sensitivity to oxidative stress, resulting in tumorigenesis or survival of cancer cells (Figure 7).

Bottom Line: We previously reported that 8-oxoguanine (8-oxoG) accumulation in nuclear DNA (nDNA) and mitochondrial DNA triggers two distinct caspase-independent cell death through buildup of single-strand DNA breaks by MutY homolog (MUTYH), an adenine DNA glycosylase.One pathway depends on poly-ADP-ribose polymerase (PARP) and the other depends on calpains.Deficiency of MUTYH causes MUTYH-associated familial adenomatous polyposis.

View Article: PubMed Central - PubMed

Affiliation: 1] Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan [2] Research Center for Nucleotide Pool, Kyushu University, Fukuoka, Japan.

ABSTRACT
p53-regulated caspase-independent cell death has been implicated in suppression of tumorigenesis, however, the regulating mechanisms are poorly understood. We previously reported that 8-oxoguanine (8-oxoG) accumulation in nuclear DNA (nDNA) and mitochondrial DNA triggers two distinct caspase-independent cell death through buildup of single-strand DNA breaks by MutY homolog (MUTYH), an adenine DNA glycosylase. One pathway depends on poly-ADP-ribose polymerase (PARP) and the other depends on calpains. Deficiency of MUTYH causes MUTYH-associated familial adenomatous polyposis. MUTYH thereby suppresses tumorigenesis not only by avoiding mutagenesis, but also by inducing cell death. Here, we identified the functional p53-binding site in the human MUTYH gene and demonstrated that MUTYH is transcriptionally regulated by p53, especially in the p53/DNA mismatch repair enzyme, MLH1-proficient colorectal cancer-derived HCT116+Chr3 cells. MUTYH-small interfering RNA, an inhibitor for p53 or PARP suppressed cell death without an additive effect, thus revealing that MUTYH is a potential mediator of p53 tumor suppression, which is known to be upregulated by MLH1. Moreover, we found that the p53-proficient, mismatch repair protein, MLH1-proficient colorectal cancer cell line express substantial levels of MUTYH in nuclei but not in mitochondria, suggesting that 8-oxoG accumulation in nDNA triggers MLH1/PARP-dependent cell death. These results provide new insights on the molecular mechanism of tumorigenesis and potential new strategies for cancer therapies.

No MeSH data available.


Related in: MedlinePlus