DNA binding by the Rad9A subunit of the Rad9-Rad1-Hus1 complex.

The Rad9-Rad1-Hus1 checkpoint clamp activates the DNA damage response and promotes DNA repair. DNA loading on the central channel of the Rad9-Rad1-Hus1 complex is required to execute its biological functions. Because Rad9A has the highest DNA affinity among the three subunits, we determined the domains and functional residues of human Rad9A that are critical for DNA interaction.

Mammalian MutY Homolog (MYH or MUTYH) is Critical for Telomere Integrity under Oxidative Stress.

Telomeres consist of special features and proteins to protect the ends of each chromosome from deterioration and fusion. The telomeric DNA repeats are highly susceptible to oxidative damage that can accelerate telomere shortening and affect telomere integrity. Several DNA repair factors including MYH/MUTYH DNA glycosylase, its interacting partners Rad9/Rad1/Hus1 checkpoint clamp, and SIRT6 aging regulator, are associated with the telomeres.

An ordered assembly of MYH glycosylase, SIRT6 protein deacetylase, and Rad9-Rad1-Hus1 checkpoint clamp at oxidatively damaged telomeres.

In the base excision repair pathway, MYH/MUTYH DNA glycosylase prevents mutations by removing adenine mispaired with 8-oxoG, a frequent oxidative lesion. MYH glycosylase activity is enhanced by Rad9-Rad1-Hus1 (9-1-1) checkpoint clamp and SIRT6 histone/protein deacetylase. Here, we show that MYH, SIRT6, and 9-1-1 are recruited to confined oxidatively damaged regions on telomeres in mammalian cells.

Chk1 inhibition as a novel therapeutic strategy in melanoma.

Melanoma patients respond poorly to chemotherapies because they acquire drug resistance. Therapies that can overcome the resistance to inhibitors of the mutated BRAF protein kinase in melanoma are urgently needed. Chk1 protein kinase is a central component of the DNA damage response and plays a crucial role in controlling cell cycle progression.

SIRT6 protein deacetylase interacts with MYH DNA glycosylase, APE1 endonuclease, and Rad9-Rad1-Hus1 checkpoint clamp.

Background: SIRT6, a member of the NAD(+)-dependent histone/protein deacetylase family, regulates genomic stability, metabolism, and lifespan. MYH glycosylase and APE1 are two base excision repair (BER) enzymes involved in mutation avoidance from oxidative DNA damage. Rad9-Rad1-Hus1 (9-1-1) checkpoint clamp promotes cell cycle checkpoint signaling and DNA repair.

Association of the Rad9-Rad1-Hus1 checkpoint clamp with MYH DNA glycosylase and DNA.

Cell cycle checkpoints provide surveillance mechanisms to activate the DNA damage response, thus preserving genomic integrity. The heterotrimeric Rad9-Rad1-Hus1 (9-1-1) clamp is a DNA damage response sensor and can be loaded onto DNA. 9-1-1 is involved in base excision repair (BER) by interacting with nearly every enzyme in BER.

Histone/protein deacetylase SIRT1 is an anticancer therapeutic target.

SIRT1, a member of the NAD(+)-dependent histone/protein deacetylase family, is involved in chromatin remodeling, DNA repair, and stress response and is a potential drug target. 5-fluorouracil (FU) and the SN1-type DNA methylating agent temozolomide (TMZ) are anticancer agents. In this study, we demonstrate that sirt1 knockout mouse embryonic fibroblast cells are more sensitive to FU and DNA methylating agents than normal cells.

Interaction of apurinic/apyrimidinic endonuclease 2 (Apn2) with Myh1 DNA glycosylase in fission yeast.

Oxidative DNA damage is repaired primarily by the base excision repair (BER) pathway in a process initiated by removal of base lesions or mismatched bases by DNA glycosylases. MutY homolog (MYH, MUTYH, or Myh1) is a DNA glycosylase which excises adenine paired with the oxidative lesion 8-oxo-7,8-dihydroguanine (8-oxoG, or G°), thus reducing G:C to T:A mutations. The resulting apurinic/apyrimidinic (AP) site is processed by an AP-endonuclease or a bifunctional glycosylase/lyase.

Mammalian MutY homolog (MYH or MUTYH) protects cells from oxidative DNA damage.

MutY DNA glycosylase homologs (MYH or MUTYH) reduce G:C to T:A mutations by removing misincorporated adenines or 2-hydroxyadenines paired with guanine or 8-oxo-7,8-dihydroguanine (8-oxo-G). Mutations in the human MYH (hMYH) gene are associated with the colorectal cancer predisposition syndrome MYH-associated polyposis. To examine the function of MYH in human cells, we regulated MYH gene expression by knockdown or overproduction.

Coordination of MYH DNA glycosylase and APE1 endonuclease activities via physical interactions.

MutY homologue (MYH) is a DNA glycosylase which excises adenine paired with the oxidative lesion 7,8-dihydro-8-oxoguanine (8-oxoG, or G(o)) during base excision repair (BER). Base excision by MYH results in an apurinic/apyrimidinic (AP) site in the DNA where the DNA sugar-phosphate backbone remains intact. A key feature of MYH activity is its physical interaction and coordination with AP endonuclease I (APE1), which subsequently nicks DNA 5' to the AP site.

Histone deacetylase SIRT1 modulates and deacetylates DNA base excision repair enzyme thymine DNA glycosylase.

TDG (thymine DNA glycosylase) is an essential multifunctional enzyme involved in DNA base excision repair, DNA demethylation and transcription regulation. TDG is the predominant enzyme that removes thymine from T/G mispair, which arises due to deamination of 5-methyl-cytosine at the CpG dinucleotide, thereby preventing C to T mutations. SIRT1 is a member of class III NAD+-dependent histone/protein deacetylases.

The role of MutY homolog (Myh1) in controlling the histone deacetylase Hst4 in the fission yeast Schizosaccharomyces pombe.

The DNA glycosylase MutY homolog (Myh1) excises adenines misincorporated opposite guanines or 7,8-dihydro-8-oxo-guanines on DNA by base excision repair thereby preventing G:C to T:A mutations. Schizosaccharomyces pombe (Sp) Hst4 is an NAD(+)-dependent histone/protein deacetylase involved in gene silencing and maintaining genomic integrity. Hst4 regulates deacetylation of histone 3 Lys56 at the entry and exit points of the nucleosome core particle.

A structural hinge in eukaryotic MutY homologues mediates catalytic activity and Rad9-Rad1-Hus1 checkpoint complex interactions.

The DNA glycosylase MutY homologue (MYH or MUTYH) removes adenines misincorporated opposite 8-oxoguanine as part of the base excision repair pathway. Importantly, defects in human MYH (hMYH) activity cause the inherited colorectal cancer syndrome MYH-associated polyposis. A key feature of MYH activity is its coordination with cell cycle checkpoint via interaction with the Rad9-Rad1-Hus1 (9-1-1) complex.

Interaction between human mismatch repair recognition proteins and checkpoint sensor Rad9-Rad1-Hus1.

In eukaryotic cells, the cell cycle checkpoint proteins Rad9, Rad1, and Hus1 form the 9-1-1 complex which is structurally similar to the proliferating cell nuclear antigen (PCNA) sliding clamp. hMSH2/hMSH6 (hMutS alpha) and hMSH2/hMSH3 (hMutS beta) are the mismatch recognition factors of the mismatch repair pathway. hMutS alpha has been shown to physically and functionally interact with PCNA.

The red wine polyphenol resveratrol reduces polycyclic aromatic hydrocarbon-induced DNA damage in MCF-10A cells.

Polycyclic aromatic hydrocarbons (PAH) are procarcinogens that can be commonly found in our food and environment. Upon biotransformation in our body system, they can cause DNA damage through the generation of genotoxic species and oxidative stress. Phase I and II enzymes are pivotal in the process of proximate carcinogen formation and elimination.

Insights into the role of Val45 and Gln182 of Escherichia coli MutY in DNA substrate binding and specificity.

Background: Escherichia coli MutY (EcMutY) reduces mutagenesis by removing adenines paired with guanines or 7,8-dihydro-8-oxo-guanines (8-oxoG). V45 and Q182 of EcMutY are considered to be the key determinants of adenine specificity. Both residues are spatially close to each other in the active site and are conserved in MutY family proteins but not in Methanobacterium thermoautotrophicum Mig.

Genistein protects against polycyclic aromatic hydrocarbon-induced oxidative DNA damage in non-cancerous breast cells MCF-10A.

Polycyclic aromatic hydrocarbons (PAH) are established cancer initiators that can be found in our food and environment. Some dietary phytochemicals are strong inhibitors of PAH-induced mutagenesis. The soya isoflavone genistein has been shown previously in our laboratory to be an inhibitor of PAH metabolite binding to DNA.

The human checkpoint sensor Rad9-Rad1-Hus1 interacts with and stimulates DNA repair enzyme TDG glycosylase.

Human (h) DNA repair enzyme thymine DNA glycosylase (hTDG) is a key DNA glycosylase in the base excision repair (BER) pathway that repairs deaminated cytosines and 5-methyl-cytosines. The cell cycle checkpoint protein Rad9-Rad1-Hus1 (the 9-1-1 complex) is the surveillance machinery involved in the preservation of genome stability. In this study, we show that hTDG interacts with hRad9, hRad1 and hHus1 as individual proteins and as a complex.

The human checkpoint sensor Rad9-Rad1-Hus1 interacts with and stimulates NEIL1 glycosylase.

The checkpoint protein Rad9/Rad1/Hus1 heterotrimer (the 9-1-1 complex) is structurally similar to the proliferating cell nuclear antigen sliding clamp and has been proposed to sense DNA damage that leads to cell cycle arrest or apoptosis. Human (h) NEIL1 DNA glycosylase, an ortholog of bacterial Nei/Fpg, is involved in repairing oxidatively damaged DNA bases. In this study, we show that hNEIL1 interacts with hRad9, hRad1 and hHus1 as individual proteins and as a complex.

Physical and functional interactions between Escherichia coli MutY glycosylase and mismatch repair protein MutS.

Escherichia coli MutY and MutS increase replication fidelity by removing adenines that were misincorporated opposite 7,8-dihydro-8-oxo-deoxyguanines (8-oxoG), G, or C. MutY DNA glycosylase removes adenines from these mismatches through a short-patch base excision repair pathway and thus prevents G:C-to-T:A and A:T-to-G:C mutations. MutS binds to the mismatches and initiates the long-patch mismatch repair on daughter DNA strands.

Functional characterization of human MutY homolog (hMYH) missense mutation (R231L) that is linked with hMYH-associated polyposis.

The MutY homolog (MYH) can excise adenines misincorporated opposite to guanines or 7,8-dihydro-8-oxo-guanines (8-oxoG) during DNA replication; thereby preventing G:C to T:A transversions. Germline mutations in the human MYH gene are associated with recessive inheritance of colorectal adenomatous polyposis (MAP). Here, we characterize one newly identified MAP-associated MYH missense mutation (R231L) that lies adjacent to the putative hMSH6 binding domain.

Physical and functional interactions between MutY glycosylase homologue (MYH) and checkpoint proteins Rad9-Rad1-Hus1.

The MYH (MutY glycosylase homologue) increases replication fidelity by removing adenines or 2-hydroxyadenine misincorporated opposite GO (7,8-dihydro-8-oxo-guanine). The 9-1-1 complex (Rad9, Rad1 and Hus1 heterotrimer complex) has been suggested as a DNA damage sensor. Here, we report that hMYH (human MYH) interacts with hHus1 (human Hus1) and hRad1 (human Rad1), but not with hRad9.

MutY and MutY homologs (MYH) in genome maintenance.

The base excision repair carried out by bacterial MutY DNA glycosylase and eukaryotic MutY homolog (MYH) is responsible for removing adenines misincorporated into DNA opposite G and 7,8-dihydro-8-oxo-guanines (8-oxoG); thereby preventing G:C to T:A mutations. Escherichia coli MutY (EcMutY) can also remove adenines from A/C and A/5-hydroxyuracil and can remove guanines from G/8-oxoG mismatches at reduced rates. Thus, MutY has a minor role in reducing the mutagenic effects on G:C to A:T transitions and G:C to C:G transversions.

Physical and functional interactions between Escherichia coli MutY and endonuclease VIII.

Both GO (7,8-dihydro-8-oxoguanine) and hoU (5-hydroxyuracil) are highly mutagenic because DNA polymerase frequently misincorporates adenine opposite these damaged bases. In Escherichia coli, MutY DNA glycosylase can remove misincorporated adenine opposite G or GO on the template strand during DNA replication. MutY remains bound to the product that contains an AP (apurinic/apyrimidinic) site.