Parthun M R, Jaehning J A
Department of Biology, Indiana University, Bloomington 47405.
Mol Cell Biol. 1992 Nov;12(11):4981-7. doi: 10.1128/mcb.12.11.4981-4987.1992.
The GAL4 activator and GAL80 repressor proteins regulate the expression of yeast genes in response to galactose. A complex of the two proteins isolated from glucose-grown cells is inactive in an in vitro transcription reaction but binds DNA and blocks activation by the GAL4-VP16 chimeric activator. The complex purified from galactose-grown cells contains a mixture of phosphorylated and unphosphorylated forms of GAL4. The galactose-induced form of GAL4 activates in vitro transcription to levels similar to those seen with GAL4-VP16. The induced GAL4 complex is indistinguishable in size and apparent shape from the uninduced complex, consistent with a continued association with GAL80. These results confirm in vivo analyses that correlate GAL4 phosphorylation with galactose induction and support a model of transcriptional activation that does not require GAL80 dissociation.
GAL4激活蛋白和GAL80阻遏蛋白可响应半乳糖调节酵母基因的表达。从在葡萄糖培养基中生长的细胞中分离出的这两种蛋白的复合物在体外转录反应中无活性，但能结合DNA并阻断GAL4-VP16嵌合激活剂的激活作用。从在半乳糖培养基中生长的细胞中纯化出的复合物含有磷酸化和未磷酸化形式的GAL4混合物。半乳糖诱导型GAL4激活体外转录的水平与GAL4-VP16的水平相似。诱导型GAL4复合物在大小和外观形状上与未诱导的复合物无法区分，这与它与GAL80持续结合一致。这些结果证实了体内分析中GAL4磷酸化与半乳糖诱导的相关性，并支持了一种不需要GAL80解离的转录激活模型。
