The Effect of DNA Damage Checkpoint on Replicative Aging in Saccharomyces cerevisiae
Date Issued
2014
Date
2014
Author(s)
Yang, Yen Kai
Abstract
Replication checkpoints serve as control mechanisms that ensure the fidelity of the replicating genome in eukaryotes. It was previously reported that a mouse model of checkpoint (ATR) deficiency exhibited replicative stress during embryogenesis, which resulted in premature aging. To further understand the role of the replication checkpoint in cellular aging, we took advantage of the ATR homologous gene MEC1 and its hypostatic gene RAD53 in yeast. We determined the replicative lifespans (RLS) of the hypomorphic mec1-100 and rad53-11 mutants; the life span of these mutants was decreased significantly as compared to the wild type strain. Therefore, we examined the genes and pathways that modulate RLS to establish the relevance of checkpoint function in cellular aging. We found that calorie restriction (CR) required the checkpoint kinase function of Mec1 and Rad53 to extend life span. We further demonstrated that checkpoint function is required to protect the stability of the rDNA array, mating loci and telomeres but this is independent of the protection by sirtuins Sir2. Moreover, while a defect in chromatin assembly (the asf1Δ mutation) did not further decrease the life span of mec1-100, it did decrease that of rad53-11. Furthermore, an increased histone supply (hir3Δ) extended the lifespan of mec1-100 cells, but not those of rad53-11. Deletion of histone acetyltransferase SAS2 results in tighter packaging of telomere and life span extension; surprisingly, mec1-100 and rad53-11 mitigate the life span extension effect of sas2Δ with the decrease being greatest in mec1-100. Collectively, our results suggest that the kinase function of Mec1 and Rad53 mediates the effect of calorie restriction on replicative life span extension. The genetic analyses reveal that the checkpoint pathway may contribute to preserving chromatin integrity in both heterochromatin (rDNA and telomere) and euchromatin (active chromatin). We propose that loss of function of the checkpoint kinase may cause aging due to failure to respond replicative stress, which increases of sporadic damage to the genome when chromatin is improperly assembled.
Subjects
DNA損害檢驗點
生殖老化
熱量限制
複製壓力
染色體重塑
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-103-R01641015-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
(MD5):2c9d15e69e3f6c9370c51578f96c7b5e