Radiation-induced double-strand breaks (DSBs) are fundamental threats to genomic integrity that result in genomic instability if not properly repaired, which can in turn lead to cancer and cell death. Although we know a great deal about the pathways of DSB repair, we know very little about how DSB repair occurs in its natural context in the cell, that is, chromatin. Chromatin by its very nature is an impediment for proteins accessing the DNA, yet the repair machinery is somehow able to navigate through the chromatin and successfully repair DNA damage. Chromatin also plays a key role in transducing the cell's response to DNA damage via the DNA damage cell cycle checkpoint. Until recently, there has been a large gap in our understanding as to how the DSB repair and the DNA damage checkpoint are influenced by the chromatin environment in mammalian cells. Integral to this process is the progression of the DNA repair machinery along a genome that is packaged into chromatin; how this occurs and the influence on the epigenome, has been a long-standing mystery. We have recently shown that chromatin is completely disassembled and reassembled during non-homologous end joining of double-strand DNA breaks in human cells. Excitingly, our recent preliminary data strongly supports an active role for dynamic chromatin assembly onto single stranded DNA (ssDNA) in the midst of homologous recombinational repair of DSBs as an intrinsic step required for DSB repair. Histones occupying ssDNA has never been reported previously in vivo, let alone their playing an important biological role. The proposed studies will uncover the nature of the histone-DNA complexes on ssDNA, and will reveal the elusive mechanism whereby chromatin assembly promotes DSB repair in human cells. By elucidating the mechanism whereby ssDNA-histone complexes contribute to DSB repair, we hope to fill significant gaps in our current knowledge of the chromosomal repair process.

Public Health Relevance

Despite the fundamental importance of maintaining genomic stability, there are still huge gaps in our knowledge of the biological processes that maintain genomic stability and the repair of radiation damage. Understanding how packaging our genome into chromatin influences these process will provide key insights into their regulation. The proposed studies will fill these knowledge gaps by uncovering the nature and role of novel intermediates in the repair process that we have uncovered, and will leverage these discoveries to identify targeted therapies to maintain genomic stability in the face of radiation.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA095641-17
Application #
10056195
Study Section
Radiation Therapeutics and Biology Study Section (RTB)
Program Officer
Fingerman, Ian M
Project Start
2002-05-01
Project End
2023-11-30
Budget Start
2020-12-01
Budget End
2021-11-30
Support Year
17
Fiscal Year
2021
Total Cost
Indirect Cost
Name
Weill Medical College of Cornell University
Department
Pathology
Type
Schools of Medicine
DUNS #
060217502
City
New York
State
NY
Country
United States
Zip Code
10065
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