Koch C, Moll T, Neuberg M, Ahorn H, Nasmyth K
Institute of Molecular Pathology, Vienna, Austria.
Science. 1993 Sep 17;261(5128):1551-7. doi: 10.1126/science.8372350.
In budding yeast genes that encode G1 cyclins and proteins involved in DNA synthesis are transcriptionally activated in late G1. A transcription factor, called SBF, is composed of Swi4 and Swi6 proteins and activates transcription of G1 cyclin genes. A different, but related, complex called MBF binds to MCB elements (Mlu I cell cycle box) found in the promoter of most DNA synthesis genes. MBF contains Swi6 and a 120-kilodalton protein (p120). MBF was purified and the gene encoding p120 (termed MBP1) was cloned. A deletion of MBP1 was not lethal but led to deregulated expression of DNA synthesis genes, indicating a direct regulatory role for MBF in MCB-driven transcription. Mbp1 is related to Swi4. Strains deleted for both MBP1 and SWI4 were inviable, demonstrating that transcriptional activation by MBF and SBF has an important role in the transition from G1 to S phase.
在出芽酵母中，编码G1细胞周期蛋白和参与DNA合成的蛋白质的基因在G1晚期被转录激活。一种名为SBF的转录因子由Swi4和Swi6蛋白组成，可激活G1细胞周期蛋白基因的转录。另一种不同但相关的复合物称为MBF，它与大多数DNA合成基因启动子中发现的MCB元件（Mlu I细胞周期盒）结合。MBF包含Swi6和一种120千道尔顿的蛋白质（p120）。MBF被纯化，编码p120的基因（称为MBP1）被克隆。MBP1的缺失并不致命，但导致DNA合成基因的表达失调，表明MBF在MCB驱动的转录中具有直接调节作用。Mbp1与Swi4相关。同时缺失MBP1和SWI4的菌株无法存活，这表明MBF和SBF的转录激活在从G1期到S期的转变中具有重要作用。
