Checkpoint proteins influence telomeric silencing and length maintenance in budding yeast.
A complex network of surveillance mechanisms, called checkpoints, interrupts cell cycle progression when damage to the genome is detected or when cells fail to complete DNA replication, thus ensuring genetic integrity. In budding yeast, components of the DNA damage checkpoint regulatory network include the RAD9, RAD17, RAD24, MEC3, DDC1, RAD53, and MEC1 genes that are proposed to be involved in different aspects of DNA metabolism. We provide evidence that some DNA damage checkpoint components play a role in maintaining telomere integrity. In fact, rad53 mutants specifically enhance repression of telomere-proximal transcription via the Sir-mediated pathway, suggesting that Rad53 might be required for proper chromatin structure at telomeres. Moreover, Rad53, Mec1, Ddc1, and Rad17 are necessary for telomere length maintenance, since mutations in all of these genes cause a decrease in telomere size. The telomeric shortening in rad53 and mec1 mutants is further enhanced in the absence of SIR genes, suggesting that Rad53/Mec1 and Sir proteins contribute to chromosome end protection by different pathways. The finding that telomere shortening, but not increased telomeric repression of gene expression in rad53 mutants, can be suppressed by increasing dNTP synthetic capacity in these strains suggests that transcriptional silencing and telomere integrity involve separable functions of Rad53.
Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, 20126 Milan, Italy. mariapia.longhese@unimib.it
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D015139:Blotting, Southern; D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics; D064447:Checkpoint Kinase 2; D002843:Chromatin / Q000235:genetics; D004249:DNA Damage / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005656:Fungal Proteins / Q000235:genetics; D020868:Gene Silencing; D005838:Genotype; D047908:Intracellular Signaling Peptides and Proteins; D009154:Mutation; D009687:Nuclear Proteins; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction; D011494:Protein Kinases / Q000235:genetics; D017346:Protein Serine-Threonine Kinases; D029701:Saccharomyces cerevisiae Proteins; D004718:Saccharomycetales / Q000235:genetics* / Q000378:metabolism*; D016615:Telomere / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic
D018797:Cell Cycle Proteins; D002843:Chromatin; D017931:DNA Primers; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; C501395:RAD17 protein, S cerevisiae; C115052:SML1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C088937:MEC1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; C513623:TEL1 protein, S cerevisiae; C067022:RAD53 protein, S cerevisiae