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The ORD1 gene encodes a transcription factor involved in oxygen regulation and is identical to IXR1, a gene that confers cisplatin sensitivity to Saccharomyces cerevisiae.

ABSTRACT: The yeast COX5a and COX5b genes encode isoforms of subunit Va of the mitochondrial inner membrane protein complex cytochrome c oxidase. These genes have been shown to be inversely regulated at the level of transcription by oxygen, which functions through the metabolic coeffector heme. In earlier studies we identified several regulatory elements that control transcriptional activation and aerobic repression of one of these genes, COX5b. Here, we report the isolation of trans-acting mutants that are defective in the aerobic repression of COX5b transcription. The mutants fall into two complementation groups. One group specifies ROX1, which encodes a product reported to be involved in transcriptional repression. The other group identified the gene we have designated ORD1. Mutations in ORD1 cause overexpression of COX5b aerobically but do not affect the expression of the hypoxic genes CYC7, HEM13, and ANB1. ORD1 mutations also do not affect the expression of the aerobic genes COX5a, CYC1, ROX1, ROX3, and TIF51A. The yeast genome contains a single ORD1 gene that resides on chromosome XI. Strains carrying chromosomal deletions of the ORD1 locus are viable and exhibit phenotypes similar to, but less severe than, that of the original mutant. The nucleotide sequence of ORD1 revealed that it is identical to IXR1, a yeast gene whose product contains two high mobility group boxes, binds to platinated DNA, and confers sensitivity to the antitumor drug cisplatin. Consistent with the latter observations, we found that the ORD1 product could bind to both the upstream region of COX5b and to DNA modified with cisplatin.

SUBMITTER: Lambert JR

PROVIDER: S-EPMC44396 | biostudies-other | 1994 Jul

REPOSITORIES: biostudies-other

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The ORD1 gene encodes a transcription factor involved in oxygen regulation and is identical to IXR1, a gene that confers cisplatin sensitivity to Saccharomyces cerevisiae.

Lambert J R JR Bilanchone V W VW Cumsky M G MG

Proceedings of the National Academy of Sciences of the United States of America 19940701 15

The yeast COX5a and COX5b genes encode isoforms of subunit Va of the mitochondrial inner membrane protein complex cytochrome c oxidase. These genes have been shown to be inversely regulated at the level of transcription by oxygen, which functions through the metabolic coeffector heme. In earlier studies we identified several regulatory elements that control transcriptional activation and aerobic repression of one of these genes, COX5b. Here, we report the isolation of trans-acting mutants that a ...[more]

PMID: 8041793

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Project description:Many fungal adhesins have short, β-aggregation-prone sequences that play important functional roles, and in the Candida albicans adhesin Als5p, these sequences cluster the adhesins after exposure to shear force. Here, we report that Saccharomyces cerevisiae flocculins Flo11p and Flo1p have similar β-aggregation-prone sequences and are similarly stimulated by shear force, despite being nonhomologous. Shear from vortex mixing induced the formation of small flocs in cells expressing either adhesin. After the addition of Ca(2+), yeast cells from vortex-sheared populations showed greatly enhanced flocculation and displayed more pronounced thioflavin-bright surface nanodomains. At high concentrations, amyloidophilic dyes inhibited Flo1p- and Flo11p-mediated agar invasion and the shear-induced increase in flocculation. Consistent with these results, atomic force microscopy of Flo11p showed successive force-distance peaks characteristic of sequentially unfolding tandem repeat domains, like Flo1p and Als5p. Flo11p-expressing cells bound together through homophilic interactions with adhesion forces of up to 700 pN and rupture lengths of up to 600 nm. These results are consistent with the potentiation of yeast flocculation by shear-induced formation of high-avidity domains of clustered adhesins at the cell surface, similar to the activation of Candida albicans adhesin Als5p. Thus, yeast adhesins from three independent gene families use similar force-dependent interactions to drive cell adhesion. IMPORTANCE The Saccharomyces cerevisiae flocculins mediate the formation of cellular aggregates and biofilm-like mats, useful in clearing yeast from fermentations. An important property of fungal adhesion proteins, including flocculins, is the ability to form catch bonds, i.e., bonds that strengthen under tension. This strengthening is based, at least in part, on increased avidity of binding due to clustering of adhesins in cell surface nanodomains. This clustering depends on amyloid-like β-aggregation of short amino acid sequences in the adhesins. In Candida albicans adhesin Als5, shear stress from vortex mixing can unfold part of the protein to expose aggregation-prone sequences, and then adhesins aggregate into nanodomains. We therefore tested whether shear stress from mixing can increase flocculation activity by potentiating similar protein remodeling and aggregation in the flocculins. The results demonstrate the applicability of the Als adhesin model and provide a rational framework for the enhancement or inhibition of flocculation in industrial applications.

Dataset Information

The ORD1 gene encodes a transcription factor involved in oxygen regulation and is identical to IXR1, a gene that confers cisplatin sensitivity to Saccharomyces cerevisiae.

Publications

The ORD1 gene encodes a transcription factor involved in oxygen regulation and is identical to IXR1, a gene that confers cisplatin sensitivity to Saccharomyces cerevisiae.

Similar Datasets

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