Expansion of trinucleotide repeat (TNR) sequences is the causative mutation for a number of hereditary diseases, including myotonic dystrophy, the most common dystrophy in adults, Fragile X syndrome, the most common form of inherited mental retardation, and neurodegenerative diseases such as Huntington's and the spinocerebellar ataxias. The mechanism of TNR instability is interesting both for understanding the etiology and inheritance of the triplet repeat diseases, and for a basic understanding of genome stability in humans. In addition, expanded CGG/CCG and CTGICAG sequences are sites of chromosome fragility, areas prone to breakage in vivo. Chromosome breakage is implicated in the generation of translocations and deletions found in many types of cancer.
The aim of this proposal is to elucidate the mechanisms involved in TNR instability and fragility, and determine how these two unusual characteristics are interrelated using Saccharomyces cerevisiae. A novel genetic assay has been developed that produces a selectable phenotype when a TNR tract expands or breaks. This assay will be used to screen for proteins whose over-expression influences TNR expansion or fragility. The proteins found to influence TNRs will be characterized to determine both their normal cellular functions and their influence on repeat maintenance. In addition, the hypothesis that TNR expansions occur by aberrant lagging strand replication will be tested by analyzing tract stability (by PCR) and fragility (by genetic and physical analysis) in specific yeast replication mutants. The role of the G2IM checkpoint in detecting TNR tract damage and preventing chromosome breakage will be investigated by comparing rates of TNR tract breakage in wild-type and cheokpoint-defective cells. Lastly, these analyses will be extended to other types of minisatellite sequences that act as fragile sites in human cells. The proposed experiments are designed to elucidate not only how simple repeats expand to cause human disease, but also the consequences of and cellular response to expanded tracts, with the goal of understanding how genomic instability can affect human health.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM063066-03
Application #
6636644
Study Section
Cell Development and Function Integrated Review Group (CDF)
Program Officer
Carter, Anthony D
Project Start
2001-05-01
Project End
2006-04-30
Budget Start
2003-05-01
Budget End
2004-04-30
Support Year
3
Fiscal Year
2003
Total Cost
$232,500
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
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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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