ROLE OF SWI4 IN CELL-CYCLE REGULATION OF CLN2 EXPRESSION
ROLE OF SWI4 IN CELL-CYCLE REGULATION OF CLN2 EXPRESSION
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DOI：
10.1128/mcb.14.7.4779
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发表时间：
1994-07-01
影响因子：
5.3
通讯作者：
TINKELENBERG, AH
中科院分区：
文献类型：
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作者：
CROSS, FR;HOEK, M;TINKELENBERG, AH
酿酒酵母CLN1和CLN2基因的表达受细胞周期调控，并可能受到正反馈的控制。有研究提出，正反馈通过Cln/Cdc28激活Swi4/Swi6转录因子，由于Swi4结合到CLN1和CLN2启动子中的特定位点（SCBs），导致CLN1和CLN2转录。为了验证这一建议，我们研究了CLN2启动子中潜在scb或SWI4基因缺失对CLN2转录控制的影响。从启动子中删除含有鉴定的SCBs的限制性片段不会阻止CLN2表达的细胞周期调节，尽管表达完全降低：细胞周期位置。含有5.5 kb质粒插入的启动子或在含有scb的限制性片段缺失点的独立2.5 kb插入的启动子也表现出细胞周期调控，因此不太可能涉及未识别的上游scb。完整CLN2启动子的细胞周期调控不需要Swi4或相关的Mbp1转录因子。相反，Swi4（而不是Mbp1）对于缺乏SCB位点的插入/删除启动子的正确细胞周期调控是必需的。我们扩展了先前的遗传证据，证明Swi4参与CLN2功能的某些方面：寻找CLN2阳性调节因子的突变只产生饱和时的Swi4突变。Swi4可能结合到CLN2启动子中的非一致序列（可能除了一致位点），或者它可能间接调节CLN2表达。
Expression of the Saccharomyces cerevisiae CLN1 and CLN2 genes is cell cycle regulated, and the genes may be controlled by positive feedback. It has been proposed that positive feedback operates via Cln/Cdc28 activation of the Swi4/Swi6 transcription factor, leading to CLN1 and CLN2 transcription due to Swi4 binding to specific sites (SCBs) in the CLN1 and CLN2 promoters. To test this proposal, we have examined the effects of deletion either of the potential SCBs in the CLN2 promoter or of the SWI4 gene on CLN2 transcriptional control. Deletion of a restriction fragment containing the identified SCBs from the promoter does not prevent cell cycle regulation of CLN2 expression, although expression is lowered at all: cell cycle positions. A promoter containing a 5.5-kb plasmid insertion or an independent 2.5-kb insertion at the point of deletion of the SCB-containing restriction fragment also exhibits cell cycle regulation, so involvement of unidentified upstream SCBs is unlikely. Neither Swi4 nor the related Mbp1 transcription factor is required for cell cycle regulation of the intact CLN2 promoter. In contrast, Swi4 (but not Mbp1) is required for correct cell cycle regulation of the insertion/deletion promoter lacking SCB sites. We have extended previous genetic evidence for involvement of Swi4 in some aspect of CLN2 function: a mutant hunt for CLN2 positive regulatory factors yielded only swi4 mutations at saturation. Swi4 may bind to nonconsensus sequences in the CLN2 promoter (possibly in addition to consensus sites), or it may act indirectly to regulate CLN2 expression.