Telomeres, the structures present at chromosomal termini, are responsible for the complete replication of the chromosomes and the protection of chromosomes against genomic instability. Most studies have centered on the addition of simple-sequence G+T sequences by the ribonucleoprotein reverse transcriptase, telomerase. Activation of telomere addition, normally through telomerase, is required for oncogenesis. However, alternative recombinational (ALT) pathways are also present in organisms ranging from yeast to humans that can substitute for telomerase. These pathways are poorly understood, leaving a gap in our understanding of telomere addition. Our long-term goal is to understand the mechanisms of both telomeric recombinational interactions, which result in the addition and deletion of telomeric sequences, and the choice between different means of elongation. The objective of this application is to use the budding yeast model system to establish the underlying principles for the regulation of Mre11 in telomere recombination. Our central hypothesis is that characterization of a novel separation-of-function allele of MRE11 wil serve as an initiation point to define the factors, pathways, and telomere states that are associated with telomere recombination. Our rationale is that increasing our knowledge of the mechanism, efficiency, and regulation of telomere recombination will ultimately provide the means for ALT manipulation in human oncogenic cells. These studies will also define the nature of epigenetic heritable states at the telomere, which may change our fundamental view of telomere structure. Recent data that is in press have led to three Specific Aims. First, we want to understand the role of two proteins that act in the same pathway with mre11-A470T: the cell-cycle protein Clb2 and the telomere-specific RFC component, Ctf18. Second, we will use model systems to test whether break-induced replication (BIR) or other mechanisms are involved in the expansion of telomere tracts. Third, we will investigate the heritable epigenetic states that are characteristic of the mre11-A470T allele. The approach is innovative in that it uses an mre11 separation-of-function allele to answer these questions. This proposal is significant because it seeks to increase our understanding of the mechanism and regulation of ALT pathways in both yeast and human systems. Insights from yeast telomere recombination will provide the blueprint for future research on vertebrate ALT cancer-associated pathways and their relationship to epigenetic states.

Public Health Relevance

The relevance of this project to the mission of the NIH is that maintenance of the termini of eukaryotic chromosomes {telomeres} is critical in preventing genomic instability, rearrangement, and oncogenesis. The proposed studies on recombinational pathways of yeast telomere addition, using a unique allele within the DNA repair protein Mre11, will lead to a better understanding of their mechanisms, and of the role of telomere structure in both oncogenesis and aging. !

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM069943-08
Application #
8438458
Study Section
Special Emphasis Panel (ZRG1-CB-N (04))
Program Officer
Carter, Anthony D
Project Start
2004-07-01
Project End
2015-03-31
Budget Start
2013-04-01
Budget End
2014-03-31
Support Year
8
Fiscal Year
2013
Total Cost
$335,850
Indirect Cost
$112,694
Name
Tulane University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
053785812
City
New Orleans
State
LA
Country
United States
Zip Code
70118
Joseph, Immanual S; Kumari, Alpana; Bhattacharyya, Mrinal K et al. (2010) An mre11 mutation that promotes telomere recombination and an efficient bypass of senescence. Genetics 185:761-70
Bhattacharyya, M K; Matthews, K M; Lustig, A J (2008) Mre11 nuclease and C-terminal tail-mediated DDR functions are required for initiating yeast telomere healing. Chromosoma 117:357-66
Bhattacharyya, Mrinal K; Lustig, Arthur J (2006) Telomere dynamics in genome stability. Trends Biochem Sci 31:114-22
Liaw, Hungjiun; Lustig, Arthur J (2006) Sir3 C-terminal domain involvement in the initiation and spreading of heterochromatin. Mol Cell Biol 26:7616-31
Williams, Bridget; Bhattacharyya, Mrinal K; Lustig, Arthur J (2005) Mre 11 p nuclease activity is dispensable for telomeric rapid deletion. DNA Repair (Amst) 4:994-1005
Joseph, Immanual; Jia, Dingwu; Lustig, Arthur J (2005) Ndj1p-dependent epigenetic resetting of telomere size in yeast meiosis. Curr Biol 15:231-7