| Summary: | 碩士 === 國立臺灣大學 === 分子與細胞生物學研究所 === 106 === Our previous studies showed that ectopic expression of Ndt80 in mitotic cells caused cells to arrest at G1 phase and prohibit DNA replication. Considering the repression of DNA replication by Ndt80 and the expression period of Ndt80 during meiosis, it was proposed that Ndt80 might be involved in repressing another round of DNA replication during the two meiotic divisions.
Our recent studies have showed that precocious expression of Ndt80 before induction for meiosis could repress pre-meiotic DNA synthesis. The repressed DNA replication was confirmed again to be pre-meiotic by the induction of Ime2. Compared to the full repression of mitotic DNA replication by Ndt80, the repression of pre-meiotic DNA replication was only partial. Since the concentration of galactose used in meiotic experiment was much less than in the cell. Therefore, we deleted the GAL1 gene to slow down galactose metabolism, and found that both the expression level of Ndt80 and the repression of pre-meiotic DNA replication by Ndt80 were increased.
Furthermore, our lab has showed that DNA re-replication occurred after pre-meiotic DNA replication in ndt80 null mutants after transient inhibition of Cdc28 activity. Nevertheless, the ndt80 null cells arrest at the pachytene stage, and we could not rule out the possibility that the DNA re-replication was due to the arrest, but not the absence of Ndt80. To clarify this problem, we constructed the cdc28-as1/cdc28-as1 ndt80Δ/ndt80Δ pIME2-CDC5/CDC5 strain which was assumed to be able to exit from pachytene arrest. The results showed that cells still performed DNA re-replication after transient inhibition of Cdc28 activity, indicating that Ndt80 is involved in regulating DNA replication during meiosis.
|
|---|
