Germline Ablation of SMUG1 DNA Glycosylase Causes Loss of 5-hydroxymethyluracil- and UNG-backup Uracil-excision Activities and Increases Cancer Predisposition of Ung-/-Msh2-/- Mice

Overview

Journal Nucleic Acids Res

Publisher Oxford University Press

Specialty Biochemistry

Date 2012 Mar 27

PMID 22447450

Citations 50

Authors

Kristin Kemmerich

Felix A Dingler

Cristina Rada

Michael S Neuberger

Affiliations

Soon will be listed here.

Abstract

Deamination of cytosine (C), 5-methylcytosine (mC) and 5-hydroxymethylcytosine (hmC) occurs spontaneously in mammalian DNA with several hundred deaminations occurring in each cell every day. The resulting potentially mutagenic mispairs of uracil (U), thymine (T) or 5-hydroxymethyluracil (hmU) with guanine (G) are substrates for repair by various DNA glycosylases. Here, we show that targeted inactivation of the mouse Smug1 DNA glycosylase gene is sufficient to ablate nearly all hmU-DNA excision activity as judged by assay of tissue extracts from knockout mice as well as by the resistance of their embryo fibroblasts to 5-hydroxymethyldeoxyuridine toxicity. Inactivation of Smug1 when combined with inactivation of the Ung uracil-DNA glycosylase gene leads to a loss of nearly all detectable uracil excision activity. Thus, SMUG1 is the dominant glycosylase responsible for hmU-excision in mice as well as the major UNG-backup for U-excision. Both Smug1-knockout and Smug1/Ung-double knockout mice breed normally and remain apparently healthy beyond 1 year of age. However, combined deficiency in SMUG1 and UNG exacerbates the cancer predisposition of Msh2(-/-) mice suggesting that when both base excision and mismatch repair pathways are defective, the mutagenic effects of spontaneous cytosine deamination are sufficient to increase cancer incidence but do not preclude mouse development.

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References

Liu P, Burdzy A, Sowers L . Substrate recognition by a family of uracil-DNA glycosylases: UNG, MUG, and TDG. Chem Res Toxicol. 2002; 15(8):1001-9. DOI: 10.1021/tx020030a. View

Darwanto A, Theruvathu J, Sowers J, Rogstad D, Pascal T, Goddard 3rd W . Mechanisms of base selection by human single-stranded selective monofunctional uracil-DNA glycosylase. J Biol Chem. 2009; 284(23):15835-46. PMC: 2708880. DOI: 10.1074/jbc.M807846200. View

Elateri I, Tinkelenberg B, Hansbury M, Caradonna S, Muller-Weeks S, Ladner R . hSMUG1 can functionally compensate for Ung1 in the yeast Saccharomyces cerevisiae. DNA Repair (Amst). 2003; 2(3):315-23. DOI: 10.1016/s1568-7864(02)00221-5. View

Pettersen H, Sundheim O, Gilljam K, Slupphaug G, Krokan H, Kavli B . Uracil-DNA glycosylases SMUG1 and UNG2 coordinate the initial steps of base excision repair by distinct mechanisms. Nucleic Acids Res. 2007; 35(12):3879-92. PMC: 1919486. DOI: 10.1093/nar/gkm372. View

Krokan H, Drablos F, Slupphaug G . Uracil in DNA--occurrence, consequences and repair. Oncogene. 2002; 21(58):8935-48. DOI: 10.1038/sj.onc.1205996. View

Wibley J, Waters T, Haushalter K, Verdine G, Pearl L . Structure and specificity of the vertebrate anti-mutator uracil-DNA glycosylase SMUG1. Mol Cell. 2003; 11(6):1647-59. DOI: 10.1016/s1097-2765(03)00235-1. View

Nilsen H, Stamp G, Andersen S, Hrivnak G, Krokan H, Lindahl T . Gene-targeted mice lacking the Ung uracil-DNA glycosylase develop B-cell lymphomas. Oncogene. 2003; 22(35):5381-6. DOI: 10.1038/sj.onc.1206860. View

Nilsen H, Haushalter K, Robins P, Barnes D, Verdine G, Lindahl T . Excision of deaminated cytosine from the vertebrate genome: role of the SMUG1 uracil-DNA glycosylase. EMBO J. 2001; 20(15):4278-86. PMC: 149160. DOI: 10.1093/emboj/20.15.4278. View

Boorstein R, Levy D, Teebor G . 5-Hydroxymethyluracil-DNA glycosylase activity may be a differentiated mammalian function. Mutat Res. 1987; 183(3):257-63. DOI: 10.1016/0167-8817(87)90008-3. View

10.

Wong E, Yang K, Kuraguchi M, Werling U, Avdievich E, Fan K . Mbd4 inactivation increases Cright-arrowT transition mutations and promotes gastrointestinal tumor formation. Proc Natl Acad Sci U S A. 2002; 99(23):14937-42. PMC: 137523. DOI: 10.1073/pnas.232579299. View

11.

Pettersen H, Visnes T, Vagbo C, Svaasand E, Doseth B, Slupphaug G . UNG-initiated base excision repair is the major repair route for 5-fluorouracil in DNA, but 5-fluorouracil cytotoxicity depends mainly on RNA incorporation. Nucleic Acids Res. 2011; 39(19):8430-44. PMC: 3201877. DOI: 10.1093/nar/gkr563. View

12.

Masaoka A, Matsubara M, Hasegawa R, Tanaka T, Kurisu S, Terato H . Mammalian 5-formyluracil-DNA glycosylase. 2. Role of SMUG1 uracil-DNA glycosylase in repair of 5-formyluracil and other oxidized and deaminated base lesions. Biochemistry. 2003; 42(17):5003-12. DOI: 10.1021/bi0273213. View

13.

Kavli B, Sundheim O, Akbari M, Otterlei M, Nilsen H, Skorpen F . hUNG2 is the major repair enzyme for removal of uracil from U:A matches, U:G mismatches, and U in single-stranded DNA, with hSMUG1 as a broad specificity backup. J Biol Chem. 2002; 277(42):39926-36. DOI: 10.1074/jbc.M207107200. View

14.

Cortazar D, Kunz C, Selfridge J, Lettieri T, Saito Y, MacDougall E . Embryonic lethal phenotype reveals a function of TDG in maintaining epigenetic stability. Nature. 2011; 470(7334):419-23. DOI: 10.1038/nature09672. View

15.

Kriaucionis S, Heintz N . The nuclear DNA base 5-hydroxymethylcytosine is present in Purkinje neurons and the brain. Science. 2009; 324(5929):929-30. PMC: 3263819. DOI: 10.1126/science.1169786. View

16.

An Q, Robins P, Lindahl T, Barnes D . C --> T mutagenesis and gamma-radiation sensitivity due to deficiency in the Smug1 and Ung DNA glycosylases. EMBO J. 2005; 24(12):2205-13. PMC: 1150883. DOI: 10.1038/sj.emboj.7600689. View

17.

Szwagierczak A, Bultmann S, Schmidt C, Spada F, Leonhardt H . Sensitive enzymatic quantification of 5-hydroxymethylcytosine in genomic DNA. Nucleic Acids Res. 2010; 38(19):e181. PMC: 2965258. DOI: 10.1093/nar/gkq684. View

18.

Sire J, Querat G, Esnault C, Priet S . Uracil within DNA: an actor of antiviral immunity. Retrovirology. 2008; 5:45. PMC: 2427051. DOI: 10.1186/1742-4690-5-45. View

19.

Popp C, Dean W, Feng S, Cokus S, Andrews S, Pellegrini M . Genome-wide erasure of DNA methylation in mouse primordial germ cells is affected by AID deficiency. Nature. 2010; 463(7284):1101-5. PMC: 2965733. DOI: 10.1038/nature08829. View

20.

Lindahl T . An N-glycosidase from Escherichia coli that releases free uracil from DNA containing deaminated cytosine residues. Proc Natl Acad Sci U S A. 1974; 71(9):3649-53. PMC: 433833. DOI: 10.1073/pnas.71.9.3649. View