Isolation and characterization of the positively acting regulatory gene QUTA from Aspergillus nidulans.

The positively acting regulator gene QUTA from Aspergillus nidulans has been identified and located within a cluster of quinic acid utilisation (QUT) genes isolated within a recombinant phage lambda (lambda Q1). The DNA sequence of the QUTA gene reveals a single uninterrupted reading frame coding for a protein of mw 90.416 Kd. The QUTA protein sequence has a protein motif in the form of a putative "DNA finger" that shows strong homology to other such motifs in the GAL4, PPR1, ARGRII, LAC9 and QA1F regulatory gene products of S. cerevisiae, K. lactis and N. crassa. The data presented confirm the view deduced by genetical analysis that the QUTA gene of A. nidulans encodes a protein capable of interacting with QUT specific DNA sequences.     

Dynamic analysis of the KlGAL regulatory system in Kluyveromyces lactis: a comparative study with Saccharomyces cerevisiae

The GAL regulatory system is highly conserved in yeast species of Saccharomyces cerevisiae and Kluyveromyces lactis. While the GAL system is a well studied system in S. cerevisiae, the dynamic behavior of the KlGAL system in K. lactis has not been characterized. Here, we have characterized the GAL system in yeast K. lactis by developing a dynamic model and comparing its performance to its not-so-distant cousin S. cerevisiae. The present analysis demonstrates the significance of the autoregulatory feedbacks due to KlGal4p, KlGal80p, KlGal1p and Lac12p on the dynamic performance of the KlGAL switch. The model predicts the experimentally observed absence of bistability in the wild type strain of K. lactis, unlike the short term memory of preculturing conditions observed in S. cerevisiae. The performance of the GAL switch is distinct for the two yeast species although they share similarities in the molecular components. The analysis suggests that the whole genome duplication of S. cerevisiae, which resulted in a dedicated inducer protein, Gal3p, may be responsible for the high sensitivity of the system to galactose concentrations. On the other hand, K. lactis uses a bifunctional protein as an inducer in addition to its galactokinase activity, which restricts its regulatory role and hence higher galactose levels in the medium are needed to trigger the GAL system. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11693-011-9082-7) contains supplementary material, which is available to authorized users.     

Identification of two proteins encoded by the Saccharomyces cerevisiae GAL4 gene.

We placed the Saccharomyces cerevisiae GAL4 gene under control of the galactose regulatory system by fusing it to the S. cerevisiae GAL1 promoter. After induction with galactose, GAL4 is now transcribed at about 1,000-fold higher levels than in wild-type S. cerevisiae. This regulated high-level expression has enabled us to tentatively identify two GAL4-encoded proteins.     

A comparative analysis of the GAL genetic switch between not-so-distant cousins: Saccharomyces cerevisiae versus Kluyveromyces lactis

Despite their close phylogenetic relationship, Kluyveromyces lactis and Saccharomyces cerevisiae have adapted their carbon utilization systems to different environments. Although they share identities in the arrangement, sequence and functionality of their GAL gene set, both yeasts have evolved important differences in the GAL genetic switch in accordance to their relative preference for the utilization of galactose as a carbon source. This review provides a comparative overview of the GAL-specific regulatory network in S. cerevisiae and K. lactis, discusses the latest models proposed to explain the transduction of the galactose signal, and describes some of the particularities that both microorganisms display in their regulatory response to different carbon sources. Emphasis is placed on the potential for improved strategies in biotechnological applications using yeasts.