SUMMARY PARAGRAPH for URA4
URA4 encodes dihydroorotase (DHOdehase), an enzyme involved in the de novo synthesis of pyrimidine ribonucleotides (shown here; 2). Ura4p catalyzes the third step in this pathway, the conversion of ureidosuccinic acid to dihydroorotate (2). Loss of Ura4p activity leads to an accumulation of ureidosuccinic acid (1) and a lack of cell growth unless uracil or uridine is added to the media (reviewed in 3).
Uracil starvation or increased levels of the pyrimidine biosynthesis pathway intermediate dihydoorotic acid (DHO) can induce URA4 expression three fold (4 and references contained therein). This regulation is mediated by the transcriptional activator Ppr1p, which binds to the UASURA site (CGGN6CCG) in the promoters of URA1, URA3, and URA4 (5). DNA-bound Ppr1p is transcriptionally inactive, but the addition of DHO converts Ppr1p to an active state that interacts with RNA polymerase II, leading to increased expression of the URA genes (5).
Last updated: 2005-12-16