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Differential regulation of two closely clustered yeast genes, MAG1 and DDI1, by cell-cycle checkpoints
1Department of Microbiology and Immunology, University of Saskatchewan, 107 Wiggins Road, Saskatoon,SK S7N 5E5, Canada.
Abstract:
Eukaryotic DNA-damage checkpoint genes have been shown to not only arrest cells at certain stages, but are also involved in the transcriptional response to DNA damage. However, while the signal transduction for cell-cycle checkpoint is well characterized, it is not clear whether the same signal transduction pathway is responsible for the regulation of all DNA damage-inducible genes. In order to understand how different checkpoint genes are involved in gene regulation, the effects of various checkpoint mutations on the expression of a unique yeast MAG1 - DDI1 dual promoter were examined in this study. MAG1 and DDI1 are transcribed from a common promoter region and co-induced by a variety of DNA damaging agents. However, gene-specific cis -acting elements were also identified, and the two genes are indeed differentially expressed under certain conditions. We found that DDI1 induction was not affected in any of the checkpoint mutants. In contrast, MAG1 induction was completely abolished in the pol2 and rad53 mutants. However, in the mec1-1 or any of the G1/S and G2/M checkpoint mutants, including rad9, rad17 and rad24, DNA damage-induced MAG1 expression was not significantly affected, and a rad9 rad17 double mutation only slightly reduced MAG1 induction. Based on this and previous studies, we present two models for the role of checkpoint genes in transcriptional regulation in response to DNA damage.
Insights
DNA damage checkpoint genes regulate gene expression. Mutations in POL2 and RAD53 abolish MAG1 gene induction, while other checkpoint mutants show no effect on MAG1 or DDI1 expression.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Eukaryotic DNA-damage checkpoint genes are crucial for cell cycle arrest and transcriptional responses to DNA damage.
- The signal transduction pathways governing cell-cycle checkpoints are well-understood, but their role in regulating DNA damage-inducible genes remains unclear.
- Understanding how specific checkpoint genes influence gene regulation is essential for comprehending DNA damage response mechanisms.
Purpose of the Study:
- To investigate the involvement of different DNA-damage checkpoint genes in transcriptional regulation.
- To examine the effects of various checkpoint mutations on the expression of the yeast MAG1-DDI1 dual promoter.
- To elucidate the differential roles of checkpoint genes in controlling the expression of co-transcribed genes.
Main Methods:
- Analysis of MAG1 and DDI1 gene expression in various yeast checkpoint mutants following DNA damage.
- Utilizing a dual promoter system to assess gene-specific regulatory elements and differential expression.
- Comparing the impact of mutations in key checkpoint genes (e.g., POL2, RAD53, MEC1, RAD9, RAD17, RAD24) on gene induction.
Main Results:
- DDI1 gene induction was unaffected by any of the tested checkpoint mutations.
- MAG1 gene induction was completely abolished in pol2 and rad53 mutants.
- MAG1 induction remained largely unaffected in mec1-1, G1/S, G2/M checkpoint mutants (rad9, rad17, rad24), and a rad9 rad17 double mutant.
Conclusions:
- The MAG1-DDI1 dual promoter system reveals differential regulation of co-transcribed genes in response to DNA damage.
- Specific checkpoint genes, such as POL2 and RAD53, play critical roles in the transcriptional induction of MAG1.
- The study proposes two models illustrating the distinct roles of checkpoint genes in the transcriptional regulation of DNA damage-inducible genes.