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Ure2 Is Involved in Nitrogen Catabolite Repression and Salt Tolerance via Ca2+ Homeostasis and Calcineurin Activation in the Yeast Hansenula polymorpha

AuthorsDominguez Olavarri, Ángel
Nitrogen metabolism
Transcription factors
Issue DateNov-2010
PublisherAmerican Society for Biochemistry and Molecular Biology
CitationJournal of Biological Chemistry 285(48): 37551-37560 (2010)
AbstractDisruption of HpURE2 resulted in a low expression of genes encoding nitrate-assimilatory proteins; sensitivity to Li+, Na+, and Cd2+; no induction of ENA1; low levels of the GATA-type transcription factor Gat1; and low intracellular Ca2+ levels. Gat1 levels were also very low in a Δcnb1 mutant lacking the regulatory subunit of calcineurin. The strain Δure2 was very sensitive to the calcineurin inhibitor FK506 and displayed several phenotypes reminiscent of Δcnb1. The reporter 4xCDRE-lacZ, containing calcineurin-dependent response elements in its promoter, revealed that calcineurin activation was reduced in HpΔure2. Expression of ScURE2 in Δure2 rescued nitrogen catabolite repression and Cd2+ tolerance but not those phenotypes depending on calcineurin activation, such as salt tolerance and nitrate assimilation gene derepression. HpΔure2 showed an increased expression of the gene PMR1 encoding the Golgi Ca2+-ATPase, whereas that of PMC1 encoding the vacuolar Ca2+-ATPase remained unaltered. PMR1 up-regulation was abolished by deletion of the GATA-type transcription factor GAT2 in a HpΔure2 genetic background, and normal Ca2+ levels were recovered. Moreover, overexpression of GAT2 or PMR1 yielded strains mimicking the phenotype of the HpΔure2. This suggests that the low Ca2+ levels in the HpΔure2 mutant are due to the high levels of Pmr1 that replenish the Golgi Ca2+ content, thus acting as a negative signal for Ca2+ entry into the cell. We conclude that HpUre2 is involved in salt tolerance and also in nitrate assimilation gene derepression via Ca2+ homeostasis regulation and calcineurin activation, which control the levels of Gat1.
Description10 páginas, 18 figuras, 2 tablas.-- et al.
Publisher version (URL)http://dx.doi.org/10.1074/jbc.M110.146902
Appears in Collections:(IBFG) Artículos
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