A gene product needed for induction of allantoin system genes in Saccharomyces cerevisiae but not for their transcriptional activation.

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RESUMO

The allantoin-degradative pathway of Saccharomyces cerevisiae consists of several genes whose expression is highly induced by the presence of allophanic acid. Induced expression requires a functional DAL81 gene product. Analysis of these genes has demonstrated the presence of three cis-acting elements in the upstream regions: (i) an upstream activation sequence (UAS) required for transcriptional activation in an inducer-independent fashion, (ii) an upstream repression sequence (URS) that mediates inhibition of this transcriptional activation, and (iii) an upstream induction sequence (UIS) needed for a response to inducer. The UIS element mediates inhibition of URS-mediated function when inducer is present. We cloned and characterized the DAL81 gene and identified the element with which it was associated. The gene was found to encode a rare 3.2-kilobase-pair mRNA. The amount of DAL81-specific RNA responded neither to induction nor to nitrogen catabolite repression. Deletion of the DAL81 gene resulted in loss of induction but did not significantly affect basal level expression of the DAL7 and DUR1,2 genes or the UAS and URS functions present in plasmid constructions. These data suggest that (i) transcriptional activation of the DAL genes and their responses to inducer are mediated by different factors and cis-acting sequences and (ii) the UIS functions only when a wild-type DAL81 gene product is available.

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