Pho4

Pho4 is a basic-helix-loop-helix (bHLH) transcription factor found in S. cerevisiae and other yeasts.

The Pho4 homodimer binds to DNA sequences containing the bHLH binding site 5'-CACGTG-3'. This sequence is found in the promoters of genes upregulated in response to phosphate availability such as the PHO5 gene.