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The role of metnase in DNA replication fork stress response and DNA damage


Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/10863

The role of metnase in DNA replication fork stress response and DNA damage

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Title: The role of metnase in DNA replication fork stress response and DNA damage
Author: De Haro, Leyma
Advisor(s): Hromas, Robert
Committee Member(s): Osley, Mary Ann
Nickoloff, Jac
Hudson, Laurie
Chackerian, Bryce
Williamson, Elizabeth
Department: University of New Mexico. Biomedical Sciences Graduate Program
Subject: Metnase
DNA replication stress
DNA damage
non-homologous end joining
replication fork
LC Subject(s): DNA replication--Regulation.
DNA damage.
Cell proliferation--Molecular aspects.
Degree Level: Doctoral
Abstract: Metnase is a recently evolved human protein with methylase (SET) and nuclease domains that is widely expressed, especially in proliferating tissues. Metnase promotes plasmid and viral DNA integration, and through an interaction with topoisomerase IIα (TopoIIα) it promotes chromosome decatenation. Metnase interacts with DNA ligase IV, promotes non-homologous end-joining (NHEJ), and repression causes mild hypersensitivity to ionizing radiation. TopoIIα has a proposed role in relaxing positive supercoils in front of replication forks. NHEJ factors have been implicated in the replication stress response. Here we show that Metnase promotes cell proliferation, but does not affect replication fork elongation as measured by cell cycle analysis, BrdU incorporation and DNA fiber analysis. Even though there is no elongation effect, Metnase confers resistance to three replication stress agents, hydroxyurea, UV light, and the topoisomerase I inhibitor, camptothecin. Metnase expression also increases the rate at which H2AX phosphorylation (a marker of stalled or collapsed replication forks) is resolved. There was no difference in formation of gamma-H2AX foci after exposure to these agents. Metnase coimmunoprecipitates (co-IP) with proliferating cell nuclear antigen (PCNA) and RAD9. Finally, we show that Metnase promotes TopoIIα-mediated relaxation of positively supercoiled DNA, similar to the torsional strain preceding replication forks. These results establish Metnase as an important component of the human replication stress response.
Graduation Date: May 2009
URI: http://hdl.handle.net/1928/10863

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