Induction and repression of the urea amidolyase gene in Saccharomyces cerevisiae.

Abstract

The DUR1,2 gene from Saccharomyces cerevisiae has been isolated on recombinant plasmids along with all DNA between the DURI,2 and MET8 loci. DUR1,2 was found to encode a 5.7-kilobase transcript, which is consistent with our earlier suggestion that the DURi and DUR2 loci are two domains of a single multifunctional gene. Steady-state levels of the DUR1,2 transcript responded to induction and nitrogen catabolite repression in the same way as urea amidolyase activity. da)81 mutants (grown with inducer) contained barely detectable amounts of DURI,2 RNA, whereas dal80 mutants (grown without inducer) contained the same amount as a wild-type induced culture. These observations support our earlier hypothesis that DUR1,2 is transcriptionally regulated, with control being mediated by the DAL80 and DAL8I gene products. We cloned the DUR1,2_Oh mutation and found it to be a Ty insertion near sequences required for complementation of durl,2 mutations.The ROAM phenotype of the DUR1,2_Oh mutation is sharply different from that of cis-dominant, DUR80 mutations, which enhance DUR1,2 expression but do not affect the normal control pattern of the gene. There is evidence that DUR80 mutations may also be Ty insertions, which generate phenotypes that are different from those in DUR1,2-Oh mutations.An appreciation for the molecular mechanisms involved in control and integration of procaryotic metabolic pathways has been gained by studying regulons with widely differing physiological functions (28, 31). Similar information is now beginning to accumulate for eucaryotic systems (42). Nitrogen catabolic systems are particularly useful for such investigations, because most are subject to multiple layers of regulation. Genes encoding the allantoin-degradative system in Saccharomyces cerevisiae, for example, respond to both induction and nitrogen catabolite repression (15,25,38 its 3-min half-life after the addition of asparagine to the medium (12). In contrast, enzyme activity is not lost after the addition of a repressive nitrogen source, but continued enzyme synthesis ceases (12). The lack of enzyme induction does not result from inducer exclusion, because daI80 mutants, which do not require the presence of an inducer for enzyme production, are similarly devoid of allantoindegrading enzymes when grown in glucose-asparagine medium (8).Earlier kinetic studies are consistent with the hypothesis that both induction and nitrogen catabolite repression are exerted at gene expression (1-4, 16, 24-26

Role of urea in microbial metabolism in aquatic systems: a biochemical and molecular review

“…SSSF porters use the energy from a sodium gradient across the cell membrane to transport the solute into the cell (Jung 2002) and are also present in higher plants, mosses, and fungi (Wang et al 2008). The DUR genes were initially identified as part of the allantoin catabolic pathway in yeast (Genbauffe & Cooper 1986) and also include the DUR1 and DUR2 genes which encode the urea carboxylase and allophanate hydrolase enzymes, respectively, discussed in further detail below. Of the phytoplankton DUR3 transporters surveyed here, the red algal lineage DUR3 amino acid sequences from the pelagophyte Aureococcus anophagefferens, the dinoflagellate Heterocapsa triquetra, and the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum group together.…”

Functional Domain Mapping and Subcellular Distribution of Dal82p in Saccharomyces cerevisiae

“…Null mutations in either of the loci result in loss of allophanate-dependent transcription (34,35). Mutations in dal81 or dal82 also result in a significant de-crease in basal level expression of the genes they regulate (35)(36)(37).…”

DAL82, a second gene required for induction of allantoin system gene transcription in Saccharomyces cerevisiae

“…Expression of several allantoin pathway genes (DAL4, DAL7, and DUR1,2) in Saccharomyces cerevisiae increases 10-to 20-fold when compounds that can be degraded to the inducer, allophanate, are added to the culture medium (4,10,36,39). A similar response is caused by the gratuitous inducer oxalurate (30).…”

“…We isolated a set of recessive mutations (dal8J) (34) that resulted in complete loss of response to induction at both the enzyme and steady-state mRNA levels (10,34,39). The dal8J locus was located on the right arm of chromosome IX by conventional genetic mapping methods (33).…”

“…A similar response is caused by the gratuitous inducer oxalurate (30). In contrast, when cells are provided with a readily used nitrogen source, such as asparagine or glutamine, mRNA levels drop precipitously whether or not inducer is present, a phenomenon termed nitrogen catabolite repression (4,10,25,36,39). cis-acting elements required for basal-level gene expression, response to inducer, and nitrogen catabolite repression have been shown to be situated upstream of the inducible DAL7 transcribed sequences, suggesting that regulation of the gene occurs at transcription (38).…”