ARE YEAST CHITIN SYNTHASES REGULATED AT THE TRANSCRIPTIONAL OR THE POSTTRANSLATIONAL LEVEL
ARE YEAST CHITIN SYNTHASES REGULATED AT THE TRANSCRIPTIONAL OR THE POSTTRANSLATIONAL LEVEL
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DOI：
10.1128/mcb.14.12.7685
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发表时间：
1994-12-01
影响因子：
5.3
通讯作者：
CABIB, E
中科院分区：
文献类型：
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作者：
CHOI, WJ;SANTOS, B;CABIB, E
酿酒酵母的三种甲壳素合成酶Chs1、Chs2和Chs3参与营养细胞的隔膜和细胞壁的形成，以及接合细胞和孢子的壁形态形成。由于合酶的性质和执行功能的时间不同，因此必须对合酶进行特定和个别的调节。通过测量萌芽和有性周期中三个合成酶和三个相应基因CHS1、CHS2和CAL1/CSD2/DIT101/KT12(以下简称CAL1/CSD2)的水平变化来研究这一调控的性质。通过在GAL1启动子的控制下将携带CHS2的细胞从含半乳糖的培养液转移到含葡萄糖的培养液中，CHS2的转录被关闭。这导致Chs2迅速消失，而信使核糖核酸的衰变要慢得多。此外，Chs2的水平在萌芽周期中经历了明显的振荡，在有性周期中下降，表明该酶在很大程度上受到合成和降解过程的调节。然而，对于CHS1和CAL1/CSD2，转录停止之后是酶原(Chs1)水平的缓慢下降或活性水平(Chs3)的增加，尽管这两种情况下的消息水平都迅速下降。在同步培养中，Chs1水平在细胞周期中是恒定的。因此，对于Chs1和Chs3，翻译后调节似乎占主导地位，可能是通过激活潜在形式。由于Chs2和Chs1一样，在细胞中以酶原形式被发现，翻译后激活步骤似乎对该合酶也是必要的。
The three chitin synthases of Saccharomyces cerevisiae, Chs1, Chs2, and Chs3, participate in septum and cell wall formation of vegetative cells and in wall morphogenesis of conjugating cells and spores. Because df the differences in the nature and in the time of execution of their functions, the synthases must be specifically and individually regulated. The nature of that regulation has been investigated by measuring changes in the levels of the three synthases and of the messages of the three corresponding genes, CHS1, CHS2, and CAL1/CSD2/DIT101/KT12 (referred to below as CAL1/CSD2), during the budding and sexual cycles. By transferring cells carrying CHS2 under the control of a GAL1 promoter from galactose-containing medium to glucose-containing medium, transcription of CHS2 was shut off. This resulted in a rapid disappearance of Chs2, whereas the mRNA decayed much more slowly. Furthermore, Chs2 levels experienced pronounced oscillations during the budding cycle and were decreased in the sexual cycle, indicating that this enzyme is largely regulated by a process of synthesis and degradation. For CHS1 and CAL1/CSD2, however, a stop in transcription was followed by a slow decrease in the level of zymogen (Chs1) or an increase in the level of activity (Chs3), despite a rapid drop in message level in both cases. In synchronized cultures, Chs1 levels were constant during the cell cycle. Thus, for Chs1 and Chs3, posttranslational regulation, probably by activation of latent forms, appears to be predominant. Since Chs2, like Chs1, is found in the cell in the zymogenic form, a posttranslational activation step appears to be necessary for this synthase also.