Maintenance of genetic stability relies not only on faithful repair of endogenous and exogenous DNA damage, but also on the prompt activation of checkpoints leading to cell cycle arrest and apoptosis, when damage exceeds a critical threshold. Spontaneous deamination of cytosine and 5-methylcytosine to uracil and thymine at CpG sites is a major mechanism of endogenous mutagenesis and plays an important role in tumorigenesis. Several uracil and thymine DNA N-glycosylases active on G: U and G: T mismatches are present in mammalian cells and protect from deamination events at CpG sites. We identified one of these enzymes, human MED1 (also known as MBD4), as an interact or of the mismatch repair (MMR) protein MLH1. Inactivation MED1 in the mouse germ line increases mutagenicity at CpG sites, but only 3-fold, raising the possibility of compensation by back-up repair activities. One such candidate is the enzyme TDG that has in vitro biochemical activities similar to MED1. Furthermore, the general MMR system may, at least in principle, act on G: T and G: U mismatches. At the moment, the relative contributions of MED1, TDG and MMR to the repair of G: U and G: T mismatches at CpG sites in vivo are unclear. Recently, we identified a novel role of MED1 in the DNA damage response to alkylating agents and other anti-tumor drugs. MED1-/- MEFs treated with increasing doses of alkylating agents, like MNNG, and other anti-tumor drugs, failed to undergo cell cycle arrest and apoptosis. Much like MMR-defective cells, resistance of MED1-/- MEFs to MNNG was due to a tolerance mechanism, as DNA damage accumulated but did not elicit a G2-M checkpoint and p53 activation. MMR proteins levels are markedly reduced in MED1-/- MEFs, suggesting that MED1 may be required for alkylating agent cytotoxicity by maintaining integrity of the MMR signaling complex. We hypothesize that MED1 has a dual role in DNA repair and DNA damage response. Experiments in this proposal are designed to: 1) characterize the role of MED1 in G2-M cell cycle arrest and apoptosis induced by DNA damage; 2) examine the role of MED1 in maintaining integrity of MMR protein levels; 3) examine the roles of MED1, TDG, and MMR in the repair of G: T mismatches at CpG sites in vivo. These studies will provide new insights into mechanisms of endogenous mutagenesis, response to DNA damage and resistance of cancer cells to anti-tumor chemotherapy. ? ?

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA078412-08
Application #
7026533
Study Section
Cancer Molecular Pathobiology Study Section (CAMP)
Program Officer
Okano, Paul
Project Start
1998-07-01
Project End
2009-02-28
Budget Start
2006-03-01
Budget End
2007-02-28
Support Year
8
Fiscal Year
2006
Total Cost
$368,125
Indirect Cost
Name
Fox Chase Cancer Center
Department
Type
DUNS #
073724262
City
Philadelphia
State
PA
Country
United States
Zip Code
19111
Weng, Yi-Lan; An, Ran; Cassin, Jessica et al. (2017) An Intrinsic Epigenetic Barrier for Functional Axon Regeneration. Neuron 94:337-346.e6
Henry, Ryan A; Mancuso, Pietro; Kuo, Yin-Ming et al. (2016) Interaction with the DNA Repair Protein Thymine DNA Glycosylase Regulates Histone Acetylation by p300. Biochemistry 55:6766-6775
Bellacosa, Alfonso; Drohat, Alexander C (2015) Role of base excision repair in maintaining the genetic and epigenetic integrity of CpG sites. DNA Repair (Amst) 32:33-42
Tricarico, Rossella; Cortellino, Salvatore; Riccio, Antonio et al. (2015) Involvement of MBD4 inactivation in mismatch repair-deficient tumorigenesis. Oncotarget 6:42892-904
Bellacosa, Alfonso (2013) Developmental disease and cancer: biological and clinical overlaps. Am J Med Genet A 161A:2788-96
Gallagher, S J; Rambow, F; Kumasaka, M et al. (2013) Beta-catenin inhibits melanocyte migration but induces melanoma metastasis. Oncogene 32:2230-8
Grigera, Fernando; Bellacosa, Alfonso; Kenter, Amy L (2013) Complex relationship between mismatch repair proteins and MBD4 during immunoglobulin class switch recombination. PLoS One 8:e78370
Slupianek, A; Falinski, R; Znojek, P et al. (2013) BCR-ABL1 kinase inhibits uracil DNA glycosylase UNG2 to enhance oxidative DNA damage and stimulate genomic instability. Leukemia 27:629-34
Li, Peng; Du, Fang; Yuelling, Larra W et al. (2013) A population of Nestin-expressing progenitors in the cerebellum exhibits increased tumorigenicity. Nat Neurosci 16:1737-44
Beeharry, Neil; Rattner, Jerome B; Bellacosa, Alfonso et al. (2012) Dose dependent effects on cell cycle checkpoints and DNA repair by bendamustine. PLoS One 7:e40342

Showing the most recent 10 out of 17 publications