Ndt80蛋白抑制DNA複製之機制
Mechanisms for repressing DNA replication by Ndt80
Date Issued
2005
Date
2005
Author(s)
Teng, Feng-Hsuan
DOI
en-US
Abstract
In Saccharomyces cerevisiae, Ndt80 is a meiosis-specific transcriptional activator that binds to the promoter element termed MSE (middle sporulation element) and induces expression of middle sporulation genes. Interestingly, ectopic expression of NDT80 in vegetative cells causes cell cycle arrest at the G1/S phase. It is possible that Ndt80 may repress another round of DNA replication between meiosis I and meiosis II, thus to successfully produce haploid spores. Repression of DNA replication by Ndt80 could be due to the induction of B-type cyclins or other unidentified genes that regulate cell cycle progression. Alternatively, it could be directly due to the binding of Ndt80 itself to the origins of DNA replication.
To distinguish between these two possibilities, we have constructed a series of in-frame deletions in the DNA-binding domain or the transcription-activation domain of Ndt80 and tested for their effects on cell cycle arrest. The results showed that the DNA-binding domain is essential for the repression at G1/S. On the other hand, the transcription-activation domain is not absolutely required for the cell cycle arrest. Furthermore, ectopic expression of NDT80 in null mutants of B-type cyclins still causes G1/S arrest, suggesting that the induction of Ndt80-regulated genes is unlikely to be the repression mechanism. However, the chromatin immunoprecipitation assays did not provide evidence for physical associations between Ndt80 and the origins of DNA replication for the direct mechanism.
Additionally, among these deletion mutations, we have isolated an interesting one, ndt80∆404-503. Based on meiotic time course analyses and further deletion analyses, we suggest that ndt80∆404-503 is a special separation-of-function mutation of NDT80 that loses the ability in repression of DNA replication but retains partial function in transcription activation.
Subjects
Ndt80
DNA複製
酵母菌
減數分裂
細胞週期
DNA replication
budding yeast
meiosis
cell cycle
Type
other
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