Our chromosomes are continually bombarded with a variety of insults, resulting in damage that must be repaired. By necessity, cells have evolved mechanisms to detect and repair broken strands of DNA, thereby preventing loss of important genetic information. Double-stranded DNA breaks (DSBs) are a type of damage that led to particularly disastrous outcomes. If not corrected, DSBs can lead to gross chromosomal rearrangements, which are the hallmark of all forms of cancer. Surprisingly, DNA replication is the primary source of DSBs. Homologous recombination (HR) is a highly conserved pathway that cells can use to repair DSBs, and HR is necessary to prevent and repair the damage that arises during DNA replication. When a DSB occurs, the DNA ends are processed to generate 3' single-strand DNA (ssDNA) overhangs. The ssDNA ends then pair with homologous sequence elsewhere in the genome, and the missing DNA sequence is replaced using the homologous DNA as a template for replication. Finally, the replicated intermediate is resolved, regenerating the continuity of the broken DNA. While seemingly simple, HR requires the coordinated action of a complex repertoire of proteins, which are responsible for sensing damage, recruiting essential factors, and processing and repairing the damaged DNA. The consequences of disrupting HR are devastating. For example, mutations in the Rad51 recombinase are embryonic lethal in mice, and mutations in human Rad51 are linked to breast cancers. In addition, defects in BRCA2 account for at least 5% of all breast cancers and also confer a genetic predisposition to ovarian cancer. BRCA2 is thought to help regulate HR, and loss of this regulation may be the reason why this gene is linked to hereditary cancers. Major new discoveries will be necessary to fully understand the mechanistic basis for these outcomes. Our overall research program is focused on understanding how (i) proteins sense and respond to damaged DNA, (ii) how DNA damage is repaired, (iii) how DNA replication can lead to damage, and (iv) how replication and recombination are linked. To help address these problems we have developed unique technologies that allow us to directly visualize hundreds of individual molecules using optical microscopy, which enables us to monitor the spatial and temporal progression of DNA repair and DNA replication in real-time at the single-molecule level. Using this approach we seek to define the fundamental mechanisms that our cells use to replicate and repair DNA, with the long-term goal of understanding how errors during these processes can lead to chromosomal rearrangements.

Public Health Relevance

Double-stranded DNA breaks (DSBs) can cause gross chromosomal rearrangements, which are the hallmark of all forms of cancer. The overall goal of our research is to study the events that lead to DSB formation and the mechanisms that cells use for DSB repair, in the hope that this research will eventually lead to a better understanding of how might be able to prevent or cure cancer.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Unknown (R35)
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Willis, Kristine Amalee
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Columbia University (N.Y.)
Schools of Medicine
New York
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De Tullio, Luisina; Kaniecki, Kyle; Greene, Eric C (2018) Single-Stranded DNA Curtains for Studying the Srs2 Helicase Using Total Internal Reflection Fluorescence Microscopy. Methods Enzymol 600:407-437
Crickard, J Brooks; Kaniecki, Kyle; Kwon, YoungHo et al. (2018) Spontaneous self-segregation of Rad51 and Dmc1 DNA recombinases within mixed recombinase filaments. J Biol Chem 293:4191-4200
Crickard, J Brooks; Kaniecki, Kyle; Kwon, YoungHo et al. (2018) Regulation of Hed1 and Rad54 binding during maturation of the meiosis-specific presynaptic complex. EMBO J 37:
Crickard, J Brooks; Kaniecki, Kyle; Kwon, Youngho et al. (2018) Meiosis-specific recombinase Dmc1 is a potent inhibitor of the Srs2 antirecombinase. Proc Natl Acad Sci U S A 115:E10041-E10048
Kaniecki, Kyle; De Tullio, Luisina; Greene, Eric C (2018) A change of view: homologous recombination at single-molecule resolution. Nat Rev Genet 19:191-207
Crickard, J Brooks; Greene, Eric C (2018) Biochemical attributes of mitotic and meiotic presynaptic complexes. DNA Repair (Amst) :
Kaniecki, Kyle; De Tullio, Luisina; Gibb, Bryan et al. (2017) Dissociation of Rad51 Presynaptic Complexes and Heteroduplex DNA Joints by Tandem Assemblies of Srs2. Cell Rep 21:3166-3177
Ma, C J; Steinfeld, J B; Greene, E C (2017) Single-Stranded DNA Curtains for Studying Homologous Recombination. Methods Enzymol 582:193-219
De Tullio, Luisina; Kaniecki, Kyle; Kwon, Youngho et al. (2017) Yeast Srs2 Helicase Promotes Redistribution of Single-Stranded DNA-Bound RPA and Rad52 in Homologous Recombination Regulation. Cell Rep 21:570-577
Zhao, Weixing; Steinfeld, Justin B; Liang, Fengshan et al. (2017) BRCA1-BARD1 promotes RAD51-mediated homologous DNA pairing. Nature 550:360-365

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