Leucine zipper Dimerization domain of Gal4p-like transcription factors
The Gal4p family of transcriptional activators contain an N-terminal DNA-binding domain with a Zn2Cys6 binuclear cluster that interact with CCG triplets and a leucine zipper-like heptad repeat that dimerizes. Dimerization allows binding of targets which contain two CCG motifs oriented in an inverted (CGG-CCG), direct (CCG-CCG), or everted (CCG-CGG) manner. Included in this family are Saccharomyces cerevisiae Gal4p, Hap1p, Put3p, Ppr1p and Sip4p, Neurospora crassa acu-15, and Colletotrichum acutatum Nir1, among others. Gal4p functions in the induction of GAL genes in the presence of galactose; GAL proteins are responsible for the transport of galactose into the cell and for its metabolism through the glycolytic pathway. Hap1p promotes transcription of genes required for respiration and controlling oxidative damage in response to heme. Put3p activates the transcription of the PUT1 and PUT2 genes in the presence of proline, allowing yeast cells to use proline as a nitrogen source. Ppr1p activates transcription of the URA1, URA3, and URA4 genes, which encode enzymes involved in the regulation of pyrimidine levels. Sip4p activates target genes under conditions of glucose deprivation. Acu-15 is involved in regulating acetate utilization while Nir1 plays a role during nitrogen-starvation conditions.
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