Mechanisms for signal transduction in the initiation of meiosis in enkaryotes

1. 我们分离出IME2， SME2和SME3基因作为减数分裂起始的正调控因子。IME2在减数分裂早期特异性转录。SME2和SME3转录本在静止细胞中积累。SME2激活SGA1的转录，SGA1是一种独立于IME1和IME2的减数分裂晚期特异性基因。SME3激活IME1转录。GAM1和GAM3是STA1的阳性调节因子，也是IME1转录所必需的。IME2的抑制需要SUD1、GAM2、NIM1和NIM2。根据这些结果，我们提出了一个控制减数分裂起始的调控级联模型。2. 利用IME2特异性抗血清，我们证实了IME2蛋白的核定位和蛋白激酶活性。由6个高酸性亚肽组成的IME2羧基末端结构域似乎具有负作用。3. 我们还研究了IME2激酶对SGA1的转录调控机制。SGA1上游5'区含有转录的正（UAS）和负（NRE）元件。IME2不调节UAS活性。NRE的缺失独立于IME2激活SGA1的转录。这些结果表明IME2激酶通过NRE解除负调控。我们还通过凝胶转移试验鉴定了UAS和nre结合蛋白。

1. We isolated IME2, SME2, and SME3 genes as positive regulators for the initiation of meiosis. IME2 was transcribed specifically at an early stage of meiosis. Transcripts from SME2 and SME3 were accumulated in stationary cells. SME2 activated transcription of SGA1, a late meiosis-specific gene, independently of IME1 and IME2. SME3 activated IME1 transcription. GAM1 and GAM3, positive regulators for STA1, were also required for transcription of IME1. SUD1, GAM2, NIM1, and NIM2 were required for repression of IME2. From these results, we proposed a model for regulatory cascades governing the initiation of meiosis. 2. Using IME2-specific antisera, we demonstrated nuclear localization and protein kinase activity of IME2 protein. Carboxy-terminal domain of IME2 consisting of six highly acidic subpeptides appeared to have a negative role. 3. We also examined the mechanism for transcriptional regulation of SGA1 by IME2 kinase. 5' upstream region of SGA1 contained positive (UAS) and negative (NRE) elements for transcription. UAS activity was not regulated by IME2. Deletion of NRE activated transcription of SGA1 independently of IME2. These results suggest that IME2 kinase relieves negative regulation through NRE. We also identified UAS- and NRE-binding proteins by gel shift assay.