Trinucleotide repeat sequences (TNRs), such as CAG/CTG repeats, expand in the human genome to cause 17 inherited human diseases, including Huntington's disease, myotonic dystrophy, and spinocerebellar ataxias. The strong hairpin-forming potential of these sequences is the likely basis for genome instability at expanded TNRs. Expanded TNRs inhibit repair of DNA gaps, interfere with DNA replication, and cause chromosomes to break (chromosome fragility). The goal of our research is to elucidate the cellular mechanisms that normally facilitate replication and repair of TNRs and determine how failure of these systems can lead to repeat expansion and chromosome breakage. We propose to characterize the role of proteins involved in DNA repair, the DNA damage checkpoint, and chromatin modification in preventing CAG/CTG repeat fragility and expansion, using Saccharomyces cerevisiae as a model system. The repair response to naturally occurring damage at strong hairpin-forming sequences will be investigated by using chromatin immunoprecipitation and fluorescence techniques to determine the identity and timing of repair protein recruitment to expanded TNRs. To establish the cellular consequences of DNA damage checkpoint activation by TNRs, division of single cells containing long CAG/CTG repeats will be monitored, and the role of the DNA damage checkpoint in preventing replication fork stalling at long repeats ascertained by 2-D gels. A novel link between TNR stability and chromatin structure will be investigated by determining the state of histone modifications and spacing at expanded TNRs. Lastly, we propose a genetic screen to identify additional proteins and pathways important in preventing chromosome fragility at CAG/CTG tracts. An understanding of how repair of CAG/CTG sequences occurs is important both to explain how repeat expansion diseases occur and to prevent pathological somatic expansions in non-dividing brain cells in Huntington's disease. Since cell death is a major factor in progression of several TNR diseases, determining the consequences of damage at expanded repeats for cell health could lead to strategies to slow disease development. The human genome contains many direct and inverted repeats and other types of sequences that present potential problems during replication and repair, so understanding the cellular mechanisms that have evolved to cope with these problems should yield important insights into genome stability. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM063066-06A1
Application #
7192315
Study Section
Molecular Genetics C Study Section (MGC)
Program Officer
Carter, Anthony D
Project Start
2001-05-01
Project End
2011-01-31
Budget Start
2007-02-01
Budget End
2008-01-31
Support Year
6
Fiscal Year
2007
Total Cost
$309,001
Indirect Cost
Name
Tufts University
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
073134835
City
Medford
State
MA
Country
United States
Zip Code
02155
Frizzell, Aisling; Nguyen, Jennifer H G; Petalcorin, Mark I R et al. (2016) RTEL1 Inhibits Trinucleotide Repeat Expansions and Fragility. Cell Rep 16:2047
House, Nealia C M; Yang, Jiahui H; Walsh, Stephen C et al. (2014) NuA4 initiates dynamic histone H4 acetylation to promote high-fidelity sister chromatid recombination at postreplication gaps. Mol Cell 55:818-828
Frizzell, Aisling; Nguyen, Jennifer H G; Petalcorin, Mark I R et al. (2014) RTEL1 inhibits trinucleotide repeat expansions and fragility. Cell Rep 6:827-35
Anand, Ranjith P; Shah, Kartik A; Niu, Hengyao et al. (2012) Overcoming natural replication barriers: differential helicase requirements. Nucleic Acids Res 40:1091-105
Cherng, Nicole; Shishkin, Alexander A; Schlager, Lucas I et al. (2011) Expansions, contractions, and fragility of the spinocerebellar ataxia type 10 pentanucleotide repeat in yeast. Proc Natl Acad Sci U S A 108:2843-8
Sundararajan, Rangapriya; Freudenreich, Catherine H (2011) Expanded CAG/CTG repeat DNA induces a checkpoint response that impacts cell proliferation in Saccharomyces cerevisiae. PLoS Genet 7:e1001339
Gellon, Lionel; Razidlo, David F; Gleeson, Olive et al. (2011) New functions of Ctf18-RFC in preserving genome stability outside its role in sister chromatid cohesion. PLoS Genet 7:e1001298
Sundararajan, Rangapriya; Gellon, Lionel; Zunder, Rachel M et al. (2010) Double-strand break repair pathways protect against CAG/CTG repeat expansions, contractions and repeat-mediated chromosomal fragility in Saccharomyces cerevisiae. Genetics 184:65-77
Yang, Jiahui H; Freudenreich, Catherine H (2010) The Rtt109 histone acetyltransferase facilitates error-free replication to prevent CAG/CTG repeat contractions. DNA Repair (Amst) 9:414-20
Kerrest, Alix; Anand, Ranjith P; Sundararajan, Rangapriya et al. (2009) SRS2 and SGS1 prevent chromosomal breaks and stabilize triplet repeats by restraining recombination. Nat Struct Mol Biol 16:159-67

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