Genetic and molecular characterisation of purine permease genes ofAspergillus nidulans reveals a novel family of transporters conserved in prokaryotes and eukaryotes

Diallinas, George; Gorfinkiel, Lisette; Arst, Herb; Cecchetto, Gianna; Scazzocchio, Claudio

doi:10.1007/bf02814078

Cited by 13 publications

(12 citation statements)

References 5 publications

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“…HpxP contains the xan_ur_permease domain present in other xanthine/uracil transporters of this family, such as UapA of Aspergillus nidulans or PbuX of Bacillus subtilis (9,18,23). Although disruption of hpxP did not modify growth on hypoxanthine or uric acid, a role of this protein as a purine transporter cannot be ruled out, since in a given organism, the existence of several nucleobase transporters that display wide substrate specificity is rather common (13,14,21). In fact, at least two genes encoding purine transporters (KPN_04013 and KPN_02555) can be identified by in silico analysis in the MGH 78578 genome.…”

Section: Discussionmentioning

confidence: 98%

The hpx Genetic System for Hypoxanthine Assimilation as a Nitrogen Source in Klebsiella pneumoniae : Gene Organization and Transcriptional Regulation

et al. 2008

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Growth experiments showed that adenine and hypoxanthine can be used as nitrogen sources by several strains of K. pneumoniae under aerobic conditions. The assimilation of all nitrogens from these purines indicates that the catabolic pathway is complete and proceeds past allantoin. Here we identify the genetic system responsible for the oxidation of hypoxanthine to allantoin in K. pneumoniae. The hpx cluster consists of seven genes, for which an organization in four transcriptional units, hpxDE, hpxR, hpxO, and hpxPQT, is proposed. The proteins involved in the oxidation of hypoxanthine (HpxDE) or uric acid (HpxO) did not display any similarity to other reported enzymes known to catalyze these reactions but instead are similar to oxygenases acting on aromatic compounds. Expression of the hpx system is activated by nitrogen limitation and by the presence of specific substrates, with hpxDE and hpxPQT controlled by both signals. Nitrogen control of hpxPQT transcription, which depends on 54 , is mediated by the Ntr system. In contrast, neither NtrC nor the nitrogen assimilation control protein is involved in the nitrogen control of hpxDE, which is dependent on 70 for transcription. Activation of these operons by the specific substrates is also mediated by different effectors and regulatory proteins. Induction of hpxPQT requires uric acid formation, whereas expression of hpxDE is induced by the presence of hypoxanthine through the regulatory protein HpxR. This LysR-type regulator binds to a TCTGC-N 4 -GCAAA site in the intergenic hpxD-hpxR region. When bound to this site for hpxDE activation, HpxR negatively controls its own transcription.

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Section: Discussionmentioning

confidence: 98%

The hpx Genetic System for Hypoxanthine Assimilation as a Nitrogen Source in Klebsiella pneumoniae : Gene Organization and Transcriptional Regulation

et al. 2008

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“…When one gene is involved in more than one step, the complete entry is shown once and only the gene symbol and database entry is shown opposite additional steps. Experimental identification of each gene is described in: nadA (Ribard et al, 2003); hxA (Glatigny and Scazzocchio, 1995); hxB (Amrani et al, 1999(Amrani et al, , 2000; xanA (Cultrone et al, 2005); uaZ ; azgA (Cecchetto et al, 2004); uapA (Gorfinkiel et al, 1993); uapC (Diallinas et al, 1995); fcyB (Vlanti and Diallinas, 2008); furD (Amillis et al, 2007;Hamari et al, 2009); furA (Hamari et al, 2009); ureA (Abreu et al, 2010); uaX and uaW are described in this article. alX (Hamari et al, 2009) aaX and the putative ureidoglycolase gene were identified by similarity with the cognate genes of S. cerevisiae, confirmed for alX and aaX by their known chromosomal locations.…”

Section: Strainsmentioning

confidence: 99%

Completing the purine utilisation pathway of Aspergillus nidulans

Gournas

Oestreicher

Amillis

et al. 2011

Fungal Genetics and Biology

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“…The UaY transcription factor mediates uric acid induction of the majority of the purine-degradation pathway genes (Scazzocchio and Darlington 1968;Scazzocchio et al 1982;Scazzocchio 1994). It is necessary for transcriptional induction of the three transporter genes uapA, uapC, and azgA (Gorfinkiel et al 1993;Diallinas et al 1995;Cecchetto et al 2004) and of structural genes involved in purine degradation: nadA (adenine deaminase, Ribard et al 2003), hxA (xanthine dehydrogenase, Glatigny and Scazzocchio 1995), hxB (MOCO sulfurase, necessary for the activity of the xanthine dehydrogenase, Amrani et al 1999), xanA (xanthine a-ketoglutaratedependent dioxygenase, Cultrone et al 2007), and uaZ (urate oxidase, . These genes are also under the positive control of the GATA factor AreA, which is active in the absence of repressive nitrogen sources (such as ammonium and glutamine, Arst and Cove 1973;Kudla et al 1990).…”

Section: T He Fungus Aspergillus Nidulans Can Use Purinesmentioning

confidence: 99%

Phenotypes of Mutations in the 5′-UTR of a Limiting Transcription Factor in Aspergillus nidulans Can Be Accounted For by Translational Inhibition and Leaky Scanning

Oestreicher¹,

Scazzocchio

2009

Genetics

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The uaY gene encodes the transcriptional activator of purine catabolism genes in Aspergillus nidulans. uaY12 results in strongly defective growth on purines as nitrogen sources and in strongly diminished transcription of UaY-regulated genes. This mutation introduces an ATG codon 64 bp upstream of the uaY ATG, generating a 68-codon open reading frame (uORFA), overlapping with the uaY ORF. uaY12 revertants fall into three categories:i. The majority eliminate the aberrant ATG. The growth and transcriptional phenotypes of these revertants are identical to those of the wild type. ii. Two revertants create a stop codon in frame with the uaY12 aberrant ATG, shortening the length of the uORFA, thus uORFA no longer overlaps the uaY ORF. The latter are partial suppressors of the uaY12 mutation, while chain termination suppressors, in turn, suppress this novel phenotype. iii. Two partial suppressors are unlinked to uaY. These two mutations result in a pleiotropic phenotype usually associated with ribosomal proteins.We hypothesize that uORFA strongly diminishes translation of the uaY ORF and that revertants negate this effect by a number of different mechanisms. The first-AUG rule and the phenomena of translational inhibition and leaky scanning provide a coherent explanation of the results presented in this article.

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Genetic and molecular characterisation of purine permease genes ofAspergillus nidulans reveals a novel family of transporters conserved in prokaryotes and eukaryotes

Cited by 13 publications

References 5 publications

The hpx Genetic System for Hypoxanthine Assimilation as a Nitrogen Source in Klebsiella pneumoniae : Gene Organization and Transcriptional Regulation

The hpx Genetic System for Hypoxanthine Assimilation as a Nitrogen Source in Klebsiella pneumoniae : Gene Organization and Transcriptional Regulation

Completing the purine utilisation pathway of Aspergillus nidulans

Phenotypes of Mutations in the 5′-UTR of a Limiting Transcription Factor in Aspergillus nidulans Can Be Accounted For by Translational Inhibition and Leaky Scanning

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