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Updated: Aug 7, 2026
Genetic Studies of Human DNA Repair Proteins Using Yeast as a Model System
Published on: March 18, 2010
The functions of budding yeast Sae2 in the DNA damage response require Mec1- and Tel1-dependent phosphorylation
Enrico Baroni1, Valeria Viscardi, Hugo Cartagena-Lirola
1Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, 20126 Milan, Italy.
Abstract:
DNA damage checkpoint pathways sense DNA lesions and transduce the signals into appropriate biological responses, including cell cycle arrest, induction of transcriptional programs, and modification or activation of repair factors. Here we show that the Saccharomyces cerevisiae Sae2 protein, known to be involved in processing meiotic and mitotic double-strand breaks, is required for proper recovery from checkpoint-mediated cell cycle arrest after DNA damage and is phosphorylated periodically during the unperturbed cell cycle and in response to DNA damage. Both cell cycle- and DNA damage-dependent Sae2 phosphorylation requires the main checkpoint kinase, Mec1, and the upstream components of its pathway, Ddc1, Rad17, Rad24, and Mec3. Another pathway, involving Tel1 and the MRX complex, is also required for full DNA damage-induced Sae2 phosphorylation, that is instead independent of the downstream checkpoint transducers Rad53 and Chk1, as well as of their mediators Rad9 and Mrc1. Mutations altering all the favored ATM/ATR phosphorylation sites of Sae2 not only abolish its in vivo phosphorylation after DNA damage but also cause hypersensitivity to methyl methanesulfonate treatment, synthetic lethality with RAD27 deletion, and decreased rates of mitotic recombination between inverted Alu repeats, suggesting that checkpoint-mediated phosphorylation of Sae2 is important to support its repair and recombination functions.
Insights
The Saccharomyces cerevisiae Sae2 protein is crucial for cell cycle recovery after DNA damage. Its phosphorylation by Mec1 and Tel1 pathways regulates DNA repair and recombination processes.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- DNA damage checkpoint pathways are essential for sensing DNA lesions and initiating cellular responses like cell cycle arrest and DNA repair.
- The Saccharomyces cerevisiae Sae2 protein is known to play a role in processing DNA double-strand breaks during meiosis and mitosis.
Purpose of the Study:
- To investigate the role of Sae2 protein in checkpoint-mediated cell cycle arrest and DNA damage recovery.
- To elucidate the mechanisms and pathways regulating Sae2 phosphorylation in response to DNA damage and during the cell cycle.
Main Methods:
- Investigated Sae2 protein phosphorylation patterns during unperturbed cell cycles and after DNA damage.
- Utilized genetic approaches involving mutations in key checkpoint and DNA repair genes (Mec1, Tel1, Ddc1, Rad17, Rad24, Mec3, Rad53, Chk1, Rad9, Mrc1, MRX complex, RAD27).
- Assessed the functional consequences of Sae2 phosphorylation site mutations on DNA damage sensitivity, synthetic lethality, and mitotic recombination.
Main Results:
- Sae2 protein is phosphorylated periodically during the cell cycle and in response to DNA damage.
- Both cell cycle- and DNA damage-dependent Sae2 phosphorylation require the Mec1 kinase and its upstream components (Ddc1, Rad17, Rad24, Mec3).
- Full DNA damage-induced Sae2 phosphorylation also involves Tel1 and the MRX complex, independent of Rad53 and Chk1.
- Mutations in Sae2 phosphorylation sites lead to DNA damage hypersensitivity, synthetic lethality with RAD27 deletion, and reduced mitotic recombination.
Conclusions:
- Checkpoint-mediated phosphorylation of Sae2 is critical for proper recovery from DNA damage-induced cell cycle arrest.
- Sae2 phosphorylation supports its functions in DNA repair and recombination processes.
- The study highlights the intricate regulation of Sae2 by multiple signaling pathways in response to DNA damage.
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