engleski

Differential effects of ser to ala mutations in the gal4 dna binding domain

The yeast transactivator Gal4 is a paradigm for studies of transcriptional activation in eukaryotes. Gal4 is known to be phosphorylated at several residues throughout the body of the protein including sites within the DNA binding domain which have yet to be precisely mapped. At least two sites, Ser 41 and Ser 47 are potential cdk consensus sites (Ser/Pro). Previous work has shown that cdk8 is required for Gal4 activation via its role in phosphorylating Ser 699. To investigate the potential role of serine phosphorylation in the Gal4 DNA binding domain we systematically mutagenized seven serines to alanine in the Gal4 DNA binding domain. Assaying transcriptional activation in vivo we found that several of the Ser to Ala mutants showed decreased transcriptional activation including Ser5, Ser22, Ser41, Ser47 and Ser85. We next examined the effect of these mutations on DNA binding in vitro and in vivo. EMSA assays showed that several of the mutants exhibit a slight decrease in DNA binding in vitro. Using CHIP assays we show that mutants exhibit a differential ability to bind the Gal4 UAS site in vivo. To address whether cdk8 is a potential kinase regulating the DNA binding domain we assayed transcriptional activation of a minimal Gal4 protein (Gal4 1-100+840-881) in a cdk8 mutant background and found that cdk8 is required for full activation by a minimal Gal4 protein lacking Ser 699.

Gal4; transcription

nije evidentirano