Primig M, Sockanathan S, Auer H, Nasmyth K
Institute of Molecular Pathology, Vienna, Austria.
Nature. 1992 Aug 13;358(6387):593-7. doi: 10.1038/358593a0.
Entry of yeast cells into the mitotic cell cycle (Start) involves a form of the CDC28 kinase that associates with G1-specific cyclins encoded by CLN1 and CLN2 (ref. 1). The onset of Start may be triggered by the activation of CLN1 and CLN2 transcription in late G1 (ref. 2). SWI4 and SWI6 are components of a factor (SBF) that binds the CACGAAAA (SCB) promoter elements responsible for activation in late G1 of the HO endonuclease, CLN1 and CLN2 genes. A related factor (MBF) containing SWI6 and a 120K protein binds to the ACGCGTNA (MCB) promoter elements responsible for late G1-specific transcription of DNA replication genes. Nothing is known about how these heteromeric proteins bind DNA. We show here that SWI4 contains a novel DNA-binding domain at its N terminus that alone binds specifically to SCBs and a C-terminal domain that binds to SWI6. SWI4's DNA-binding domain is similar to an N-terminal domain of the cdc10 protein that is a component of an MBF-like factor from Schizosaccharomyces pombe and is required for Start. An involvement of this kind of DNA-binding domain in transcriptional controls at Start may therefore be a conserved feature of eukaryotic cells.
酵母细胞进入有丝分裂细胞周期（起始阶段）涉及一种CDC28激酶形式，它与由CLN1和CLN2编码的G1期特异性细胞周期蛋白相关联（参考文献1）。起始阶段的开始可能由G1晚期CLN1和CLN2转录的激活所触发（参考文献2）。SWI4和SWI6是一个因子（SBF）的组成部分，该因子结合负责在G1晚期激活HO核酸内切酶、CLN1和CLN2基因的CACGAAAA（SCB）启动子元件。一个包含SWI6和一种120K蛋白的相关因子（MBF）与负责DNA复制基因G1晚期特异性转录的ACGCGTNA（MCB）启动子元件结合。关于这些异源蛋白如何结合DNA尚不清楚。我们在此表明，SWI4在其N末端含有一个新的DNA结合结构域，该结构域单独就能特异性结合SCB，并且在C末端有一个与SWI6结合的结构域。SWI4的DNA结合结构域类似于cdc10蛋白的N末端结构域，cdc10蛋白是粟酒裂殖酵母中一种类似MBF因子的组成部分，是起始阶段所必需的。因此，这种DNA结合结构域参与起始阶段的转录调控可能是真核细胞的一个保守特征。
