A transcriptionally active form of GAL4 is phosphorylated and associated with GAL80.
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.
Parthun
M R
MR
Department of Biology, Indiana University, Bloomington 47405.
Jaehning
J A
JA
D001483:Base Sequence; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000302:isolation & purification / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D008969:Molecular Sequence Data; D010766:Phosphorylation; D012319:RNA Polymerase II / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; C055002:GAL80 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D012319:RNA Polymerase II