Genome integrity is constantly threatened by environmental exposure to genotoxins. Many genotoxins induce replication stress and cause replication fork stalling at genomic regions that are highly sensitive to replication stress. Stalld replication can lead to DNA lesions or rearrangements that are detrimental to genome stability. Therefore, repair pathways have evolved to counter replication-stress-induced genome instability. Not surprisingly, defects in replication-stress-response proteins give rise to disease that extend beyond cancer. Efficient restart and repair of stalled replication has recently been recognized as one of the most important mechanisms for preserving genome stability. Therefore, understanding how stalled replication is restarted/repaired is fundamentally important for understanding how cells repair DNA damages caused by genotoxins and the role of fork stalling in modulating early events in carcinogenesis. However, the mechanism underlying fork restart is poorly defined, and many factors critical for fork restart remain unidentified. This application focuses on understanding the role of a newly-identified player in countering replication stress. The CST complex, consisting of Ctc1, Stn1, Ten1, is a conserved high-affinity single-stranded DNA binding protein complex. Recent studies have shown that deficiency in CST impairs the restart of stalled replication genome- wide and induces DNA damage in the genomic region. However, its role in restarting stalled replication has not been characterized. The objective of this proposal is to understand the role of CST in preserving genome stability under replication stress, with the goal to provide novel insights into how cells counteract DNA damage caused by genotoxin-induced replication stress. We will map sequences protected by CST genome-wide, characterize chromosome instabilities caused by CST deficiency under replication stress, ascertain how CST interplays with the known fork-restart players to rescue stalled replication, and determine the role of post- translational phosphorylation of Stn1 in restarting stalled replication. This will be accomplished by integration of ChIP-seq, mass spectrometry, fluorescent DNA fiber analysis, molecular and biochemical methods. Findings from the proposed research will reveal novel information of rescuing stalled replication and preserving genome stability.

Public Health Relevance

Maintenance of genome stability is essential for preventing diseases including early aging, cancer, neurological diseases, and other complex diseases. There is growing evidence that environmental agents induce replication stress that result in DNA lesions and genome instability. This proposal aims to yield new insights into how replication stress is countered by cellular machineries, and may lead to new targets for improved therapies.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Cancer Etiology Study Section (CE)
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Willis, Kristine Amalee
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Washington State University
United States
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Jia, Pingping; Chai, Weihang (2018) The MLH1 ATPase domain is needed for suppressing aberrant formation of interstitial telomeric sequences. DNA Repair (Amst) 65:20-25
Wang, Yuan; Chai, Weihang (2018) Pathogenic CTC1 mutations cause global genome instabilities under replication stress. Nucleic Acids Res 46:3981-3992
Huang, Chenhui; Jia, Pingping; Chastain, Megan et al. (2017) The human CTC1/STN1/TEN1 complex regulates telomere maintenance in ALT cancer cells. Exp Cell Res 355:95-104
Chastain, Megan; Zhou, Qing; Shiva, Olga et al. (2016) Human CST Facilitates Genome-wide RAD51 Recruitment to GC-Rich Repetitive Sequences in Response to Replication Stress. Cell Rep 16:1300-1314
Zhou, Qing; Chai, Weihang (2016) Suppression of STN1 enhances the cytotoxicity of chemotherapeutic agents in cancer cells by elevating DNA damage. Oncol Lett 12:800-808
Jia, Pingping; Chastain, Megan; Zou, Ying et al. (2016) Human MLH1 suppresses the insertion of telomeric sequences at intra-chromosomal sites in telomerase-expressing cells. Nucleic Acids Res :
Jia, Pingping; Her, Chengtao; Chai, Weihang (2015) DNA excision repair at telomeres. DNA Repair (Amst) 36:137-45
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