A comparison of the S. cerevisiae and S.pombe PHO signaling pathways. (A) A schematic depicting the PHO signaling pathway in S. cerevisiae. In conditions where Pi is plentiful (high Pi, left) Pho4 is multiply phosphorylated by the Pho85-Pho80 complex and is excluded from the nucleus. Depletion of inorganic phosphate (no Pi, right) leads to the IP7-Pho81-dependent inhibition of Pho85-Pho80. Relief of Pho85-Pho80 mediated repression allows unphosphorylated Pho4 to enter the nucleus, interact with Pho2 at PHO-specific genes, and induce transcription. (B) A schematic depicting the PHO signaling pathway in S. pombe. In high Pi conditions (left) some Pho7 is bound to the promoters of Pi- and pho7+-dependent genes. Bound Pho7 is prevented from reaching maximal activation by the repressive effects of Csk1. Loss of external phosphate (right) results in the recruitment of additional Pho7 to the promoter and the relief of Csk1-mediated repression. The Pho7-dependent genes identified in this study that are regulated in this manner are listed (S. cerevisiae orthologs in parenthesis).
Carter-O’Connell et al. BMC Genomics 2012 13:697 doi:10.1186/1471-2164-13-697