Long R M, Mylin L M, Hopper J E
Department of Biological Chemistry, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033.
Mol Cell Biol. 1991 Apr;11(4):2311-4. doi: 10.1128/mcb.11.4.2311-2314.1991.
The GAL4 protein of Saccharomyces cerevisiae is a DNA-binding transcriptional activator that is highly specific for the GAL genes. In vivo levels of GAL gene transcription are closely correlated with the phosphorylation state of GAL4. In vivo levels of GAL gene transcription are also affected by the activity of the GAL11 (SPT13) protein, a protein that has been implicated as a global auxiliary transcriptional factor. Here we examine the influence of GAL11 (SPT13) on the phosphorylation state of GAL4. Cells bearing a gal11 deletion mutation are defective in the production or maintenance of GAL4III, a phosphorylated form of GAL4 that is associated with higher levels of GAL gene transcription. In addition, the gal11 deletion cells are reduced in total GAL4 protein. However, the fivefold-reduced expression of the GAL1 gene observed in gal11 deletion cells cannot be due solely to reduced levels of total GAL4 protein, since gal11 deletion cells amplified for GAL4 production are still markedly reduced in GAL4 protein-dependent transcription. Thus, these data demonstrate that the GAL11 protein augments GAL4 protein-dependent transcription in a manner that is tightly coupled to the formation or maintenance of a phosphorylated form of GAL4.
酿酒酵母的GAL4蛋白是一种对GAL基因具有高度特异性的DNA结合转录激活因子。GAL基因转录的体内水平与GAL4的磷酸化状态密切相关。GAL基因转录的体内水平也受GAL11（SPT13）蛋白活性的影响，该蛋白被认为是一种全局辅助转录因子。在这里，我们研究了GAL11（SPT13）对GAL4磷酸化状态的影响。携带gal11缺失突变的细胞在GAL4III（一种与较高水平的GAL基因转录相关的GAL4磷酸化形式）的产生或维持方面存在缺陷。此外，gal11缺失细胞中的总GAL4蛋白减少。然而，在gal11缺失细胞中观察到的GAL1基因表达降低五倍不能仅仅归因于总GAL4蛋白水平的降低，因为为GAL4产生而扩增的gal11缺失细胞在依赖GAL4蛋白的转录中仍然显著降低。因此，这些数据表明，GAL11蛋白以一种与GAL4磷酸化形式的形成或维持紧密相关的方式增强依赖GAL4蛋白的转录。
