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Qri2/Nse4, a component of the essential Smc5/6 DNA repair complex
Bin Hu1, Chunyan Liao, Stefan H Millson
1Department of Life Sciences, King's College London, London SE1 9NN, UK.
Abstract:
We demonstrate a role for Qri2 in the essential DNA repair function of the Smc5/6 complex in Saccharomyces cerevisiae. We generated temperature-sensitive (ts) mutants in QRI2 and characterized their properties. The mutants arrest after S phase and prior to mitosis. Furthermore, the arrest is dependant on the Rad24 checkpoint, and is also accompanied by phosphorylation of the Rad53 checkpoint effector kinase. The mutants also display genome instability and are sensitive to agents that damage DNA. Two-hybrid screens reveal a physical interaction between Qri2 and proteins that are non-Smc elements of the Smc5/6 DNA repair complex, which is why we propose the name NSE4 for the open reading frame previously known as QRI2. A key role for Nse4 in Smc5/6 function is likely, as overexpressing known subunits of the Smc5/6 complex suppresses nse4(ts) cell cycle arrest. The nse4(ts) growth arrest is non-lethal and unlike the catastrophic nuclear fragmentation phenotype of smc6(ts) mutants, the nucleus remains intact; replicative intermediates and sheared DNA are not detected. This could imply a role for Nse4 in maintenance of higher order chromosome structure.
Insights
Qri2, now named Nse4, is crucial for DNA repair in Saccharomyces cerevisiae's Smc5/6 complex. Nse4 deficiency causes cell cycle arrest and genome instability, highlighting its essential role in maintaining chromosome structure.
Area of Science:
- * Molecular and Cellular Biology
- * Genetics and Genomics
- * DNA Repair Mechanisms
Background:
- * The Smc5/6 complex is vital for genome stability and DNA repair.
- * The precise function of all Smc5/6 complex subunits is not fully elucidated.
Purpose of the Study:
- * To investigate the role of Qri2 in the Smc5/6 DNA repair complex.
- * To characterize the function of Qri2 within Saccharomyces cerevisiae.
Main Methods:
- * Generation and characterization of temperature-sensitive (ts) mutants for QRI2.
- * Cell cycle analysis, checkpoint assays (Rad24, Rad53), and sensitivity testing to DNA damaging agents.
- * Two-hybrid screens to identify protein interactions.
Main Results:
- * Qri2 (renamed Nse4) mutants exhibit S phase arrest dependent on the Rad24 checkpoint and Rad53 phosphorylation.
- * Nse4 mutants display genome instability and sensitivity to DNA damaging agents.
- * Nse4 physically interacts with non-Smc components of the Smc5/6 complex, and its overexpression rescues the cell cycle arrest.
Conclusions:
- * Qri2, designated Nse4, is an essential component of the Smc5/6 DNA repair complex in Saccharomyces cerevisiae.
- * Nse4 plays a critical role in DNA repair, cell cycle progression, and potentially in maintaining higher-order chromosome structure.
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