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Ying HeFollow

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program


Year Degree Awarded


Month Degree Awarded


First Advisor

John M. Lopes

Second Advisor

Steven Sandler

Third Advisor

Kevin Griffith

Fourth Advisor

Samuel Hazen


The Saccharomyces cerevisiae PHO5 gene product accounts for a majority of the acid phosphatase activity. Its expression is induced by the basic helix-loop-helix (bHLH) protein, Pho4p, in response to phosphate depletion. Pho4p binds predominantly to two UAS elements (UASp1 at -356 and UASp2 at -247) in the PHO5 promoter. Previous studies from our lab have shown cross-regulation of different biological processes by bHLH proteins. This study tested the ability of all yeast bHLH proteins to regulate PHO5 expression and identified inositol-mediated regulation via the Ino2p/Ino4p bHLH proteins. Ino2p/Ino4p are known regulators of phospholipid biosynthetic genes. Genetic epistasis experiments showed that regulation of PHO5 by inositol required a third UAS site (UASp3 at -194). ChIP assays showed that Ino2p:Ino4p bind the PHO5 promoter. These results demonstrate that phospholipid biosynthesis is coordinated with phosphate utilization via the bHLH proteins.