High impact information on RPT3

• The genes YNT1, YNR1 and YNI1, encoding respectively nitrate transport, nitrate reductase and nitrite reductase, have been cloned, as well as two other genes encoding transcriptional regulatory factors [1].
• In the yeast Hansenula polymorpha, the YNT1 gene encodes the high affinity nitrate transporter, which is repressed by reduced nitrogen sources such as ammonium or glutamine [2].
• We conclude that glutamine triggers Ynt1 down-regulation via ubiquitinylation of lysines in the central hydrophilic domain, and proteolysis in the vacuole [2].
• Ynt1-green fluorescent protein chimera and a mutant defective in vacuolar proteinase A (Deltapep4) showed that Ynt1 is degraded in the vacuole in response to glutamine [2].
• The central hydrophilic domain of Ynt1 contains PEST-like sequences whose deletion blocked Ynt1 down-regulation [2].

Biological context of RPT3

• YTA1 and YTA2 are essential genes in yeast [3].
• The growth phenotypes and morphological alterations evident in these mutant yeast can be compensated by a mutation in YNT1, an essential gene in yeast [4].
• Clustering of the YNA1 gene encoding a Zn(II)2Cys6 transcriptional factor in the yeast Hansenula polymorpha with the nitrate assimilation genes YNT1, YNI1 and YNR1, and its involvement in their transcriptional activation [5].
• To assess the role of NR in nitrate-assimilatory gene expression, different strains lacking YNR1, or both YNR1 and YNT1 (high-affinity nitrate transporter) genes, or expressing the tobacco NR under the YNR1 promoter, were used [6].

Associations of RPT3 with chemical compounds

• Ynt1-ubiquitin conjugates were induced by glutamine and not nitrate [2].
• Ynt1 protein is degraded in response to glutamine in the growth medium [2].
• Ynt1 failed to transport chlorate and, as a result, strains lacking YNT1 were sensitive to chlorate, as is the wild-type [7].

Other interactions of RPT3

• Ynt1p is more distantly related to Yme1p [4].
• Likewise, nitrate uptake detected in the strain FM31 is independent of both Ynt1p and Yna1p and is not affected by ammonium, glutamine or chlorate [8].

Analytical, diagnostic and therapeutic context of RPT3

• Site-directed mutagenesis showed that Lys-253 and Lys-270, located in this sequence, were involved in internalization and subsequent vacuolar degradation of Ynt1 [2].
• Northern-blot analysis showed that YNT1 is expressed when the yeast is grown in nitrate and nitrite but not in ammonium solution [9].

References