Instability of chromosomal fragile sites is directly related to many cancers. Three types of fragile sites are generated under three different culture conditions: FRA3B, an aphidicolin-inducible fragile site, FRA11B, a folate-sensitive site, and FRA16B, a distamycin-A-inducible site, are involved in the formation of cancers. Compact chromatin structures and unusual DNA sequences have been found in fragile sites. Also, fragile sites display replication delay and can escape the ATR-dependent replication checkpoint. These observations provide an intriguing model for the nature of fragile sites, in which chromatin and DNA structures at these sites would pause the progress of the replication fork, and disrupt cell cycle checkpoint pathways to allow chromosomal rearrangement and viral integration, resulting in fragile site-specific tumorigenesis. Three goals are proposed: (1) Identify unique determinants for the fragile site-specific chromatin. Chromatin immunoprecipitation (CHIP) assays will be employed to identify epigenetic marks involved in these sites. Further, by reconstituting chromatin over all three fragile DNAs, fragile site-specific chromatin structure will be analyzed, and the essential components involved in the formation of fragile chromatin will be identified. (2) Establish cell cycle checkpoint pathways involved in the expression of fragile sites. Using CHIP assay and mutant cells created by RNA interference, the involvement of several cell cycle checkpoint proteins in the expression of fragile sites will be examined for their association with fragile DNA. (3) Determine cis- and trans-factors affecting fragile site instability by using an SV40 replication model system. By manipulating fragile DNA (length, sequences, replication direction, and location relative to replication origin) and cell cycle checkpoint components, fragile site instability (generation of break sites and changes in repeat length) will be evaluated. Replication intermediates containing fragile DNAs will also be characterized to provide direct information about replication delay of fragile sites. This proposal addresses how fragile sites lead to oncogenic lesions at three sequential steps. Therefore, these experiments will further advance knowledge about the nature of these fragile sites and their role in the formation of cancer, and also address fundamental biological questions, such as determinants of chromatin structure. ? ?

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
Project #
Application #
Study Section
Cancer Etiology Study Section (CE)
Program Officer
Pelroy, Richard
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Wake Forest University Health Sciences
Schools of Medicine
United States
Zip Code
Dillon, Laura W; Lehman, Christine E; Wang, Yuh-Hwa (2012) The role of fragile sites in sporadic papillary thyroid carcinoma. J Thyroid Res 2012:927683
Reddy, Kaalak; Tam, Mandy; Bowater, Richard P et al. (2011) Determinants of R-loop formation at convergent bidirectionally transcribed trinucleotide repeats. Nucleic Acids Res 39:1749-62
Weckerle, Allison B; Santra, Madhumita; Ng, Maggie C Y et al. (2011) CBFB and MYH11 in inv(16)(p13q22) of acute myeloid leukemia displaying close spatial proximity in interphase nuclei of human hematopoietic stem cells. Genes Chromosomes Cancer 50:746-55
Burrow, Allison A; Marullo, Allison; Holder, Lindsay R et al. (2010) Secondary structure formation and DNA instability at fragile site FRA16B. Nucleic Acids Res 38:2865-77
Wan, Cheng; Kulkarni, Atul; Wang, Yuh-Hwa (2010) ATR preferentially interacts with common fragile site FRA3B and the binding requires its kinase activity in response to aphidicolin treatment. Mutat Res 686:39-46
Hagerman, Katharine A; Ruan, Haihe; Edamura, Kerrie Nichol et al. (2009) The ATTCT repeats of spinocerebellar ataxia type 10 display strong nucleosome assembly which is enhanced by repeat interruptions. Gene 434:29-34
Burrow, Allison A; Williams, Laura E; Pierce, Levi C T et al. (2009) Over half of breakpoints in gene pairs involved in cancer-specific recurrent translocations are mapped to human chromosomal fragile sites. BMC Genomics 10:59
Kar, Karunakar; Wang, Yuh-Hwa; Brodsky, Barbara (2008) Sequence dependence of kinetics and morphology of collagen model peptide self-assembly into higher order structures. Protein Sci 17:1086-95
Wang, Yuh-Hwa (2007) Chromatin structure of repeating CTG/CAG and CGG/CCG sequences in human disease. Front Biosci 12:4731-41
Trojer, Patrick; Li, Guohong; Sims 3rd, Robert J et al. (2007) L3MBTL1, a histone-methylation-dependent chromatin lock. Cell 129:915-28

Showing the most recent 10 out of 17 publications