duf89Δ derepression of Pho1 expression depends on inositol 1-pyrophosphate synthesis and the Pol2 CTD Thr4 mark. (A) Growth of S. pombe strains with the indicated duf89, asp1, and rpb1 alleles. Cells were inoculated in YES broth and grown at 30°C. Exponentially growing cultures were adjusted to A600 of 0.1 and aliquots (3 µL) of serial fivefold dilutions were spotted on YES agar and then incubated at the temperatures specified. (B) The indicated fission yeast strains were grown to A600 of 0.5 to 0.8 in liquid culture in YES medium at 30°C. Cells were then harvested, washed with water, and assayed for Pho1 acid phosphatase activity by conversion of p-nitrophenylphosphate to p-nitrophenol. Activity is expressed as the ratio of A410 (p-nitrophenol production) to A600 (input cells). (C) Structures of 5-IP7 and 1,5-IP8 are shown. Asp1 kinase converts 5-IP7 to IP8 and the Asp1 pyrophosphatase reverses this process.
