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Tof1p regulates DNA damage responses during S phase in Saccharomyces cerevisiae
1Division of Basic Sciences, A3-023, Fred Hutchinson Cancer Research Center, 1100 Faiorview Ave., Seattle, WA 98109-1024, USA. efoss@fred.fhcrc.org
Abstract:
A tof1 mutant was recovered in a screen aimed at identifying genes involved specifically in the S phase branch of the MEC1-dependent DNA damage response pathway. The screen was based on the observation that mutants missing this branch are particularly dependent on the cell cycle-wide branch and, therefore, on RAD9, for surviving DNA damage. tof1 and rad9 conferred synergistic sensitivity to MMS, UV, and HU, and the double mutant was incapable of slowing S phase in response to MMS, inducing RNR3 transcription in response to UV, and phosphorylating Rad53p in response to HU. TOF1's contribution to DNA damage response appeared to be restricted to S phase, since TOF1 did not contribute to UV-induced transcription during G1 or to the cdc13-1-induced block to anaphase in G2/M. I suggest a model in which Tof1p functions to link Mec1p with Rad53p.
Insights
The study identified TOF1 as a key gene in the S phase DNA damage response. Tof1p acts as a crucial link between Mec1p and Rad53p for cell survival after DNA damage.
Area of Science:
- Molecular Biology
- Cell Cycle Regulation
- DNA Damage Response
Background:
- The DNA damage response is critical for maintaining genomic integrity.
- The MEC1 pathway regulates DNA damage responses, with distinct S phase and cell cycle-wide branches.
- Mutants lacking the S phase branch heavily rely on the RAD9-dependent cell cycle-wide branch for survival.
Purpose of the Study:
- To identify genes specifically involved in the S phase branch of the MEC1-dependent DNA damage response.
- To elucidate the role of the novel mutant TOF1 in DNA damage tolerance.
Main Methods:
- Genetic screening to identify mutants sensitive to DNA damaging agents.
- Analysis of synergistic sensitivity to methyl methanesulfonate (MMS), UV radiation, and hydroxyurea (HU) in single and double mutants.
- Assessment of cell cycle progression, gene transcription, and protein phosphorylation in response to DNA damage.
Main Results:
- A tof1 mutant was isolated, exhibiting synergistic sensitivity with rad9 to MMS, UV, and HU.
- The tof1 rad9 double mutant failed to slow S phase after MMS, induce RNR3 transcription after UV, and phosphorylate Rad53p after HU.
- TOF1's role in DNA damage response was confined to S phase, not affecting G1 or G2/M phases.
Conclusions:
- TOF1 is essential for the S phase-specific DNA damage response pathway.
- Tof1p likely functions by connecting Mec1p and Rad53p within the DNA damage response network.
- Understanding TOF1's role provides insights into maintaining cell viability during DNA replication stress.