Disruption of Histone Deacetylase Gene RPD3 Accelerates PHO5 Activation Kinetics through Inappropriate Pho84p Recycling

Abstract

ABSTRACT The histone deacetylase Rpd3p functions as a transcriptional repressor of a diverse set of genes, including PHO5 . Here we describe a novel role for RPD3 in the regulation of phosphate transporter Pho84p retention in the cytoplasmic membrane. We show that under repressing conditions (with P i ), PHO5 expression is increased in a pho4Δ rpd3Δ strain, demonstrating PHO regulatory pathway independence. However, the effect of RPD3 disruption on PHO5 activation kinetics is dependent on the PHO regulatory pathway. Upon switching to activating conditions (without P i ), PHO5 transcripts accumulated more rapidly in rpd3Δ cells. This more rapid response correlates with a defect in phosphate uptake due to premature recycling of Pho84p, the high-affinity H + /PO 4 3− symporter. Thus, RPD3 also participates in PHO5 regulation through a previously unidentified effect on maintenance of high-affinity phosphate uptake during phosphate starvation. We propose that Rpd3p has a negative role in the regulation of Pho84p endocytosis.