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A transcription factor cascade involving Fep1 and the CCAAT-binding factor Php4 regulates gene expression in response to iron deficiency in the fission yeast Schizosaccharomyces pombe.

ABSTRACT: We have identified genes encoding candidate proteins involved in iron storage (pcl1+), the tricarboxylic acid cycle (sdh4+), and iron-sulfur cluster assembly (isa1+) that are negatively regulated in response to iron deprivation. Promoter deletion and site-directed mutagenesis permitted identification of a new cis-regulatory element in the promoter region of the pcl1+ gene. This cis-acting regulatory sequence containing the pentanucleotide sequence CCAAT is responsible for transcriptional repression of pcl1+ under low iron supply conditions. In Schizosaccharomyces pombe, the CCAAT-binding factor is a heteromeric DNA-binding complex that contains three subunits, designated Php2, Php3, and Php5. Inactivation of the php2+ locus negatively affects the transcriptional competency of pcl1+. A fourth subunit, designated Php4, is not essential for the transcriptional activation of target genes under basal and iron-replete conditions. We demonstrate that, in response to iron-limiting conditions, Php4 is required for down-regulation of pcl1+, sdh4+, and isa1+ mRNA levels. In vivo RNase protection studies reveal that the expression of php4+ is negatively regulated by iron and that this regulated expression requires a functional fep1+ gene. The results of these studies reveal that Fep1 represses php4+ expression in response to iron. In contrast, when iron is scarce, Fep1 becomes inactive and php4+ is expressed to act as a regulatory subunit of the CCAAT-binding factor that is required to block pcl1+, sdh4+, and isa1+ gene transcription.

SUBMITTER: Mercier A

PROVIDER: S-EPMC1694796 | biostudies-literature | 2006 Nov

REPOSITORIES: biostudies-literature

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A transcription factor cascade involving Fep1 and the CCAAT-binding factor Php4 regulates gene expression in response to iron deficiency in the fission yeast Schizosaccharomyces pombe.

Mercier Alexandre A Pelletier Benoit B Labbé Simon S

Eukaryotic cell 20060908 11

We have identified genes encoding candidate proteins involved in iron storage (pcl1+), the tricarboxylic acid cycle (sdh4+), and iron-sulfur cluster assembly (isa1+) that are negatively regulated in response to iron deprivation. Promoter deletion and site-directed mutagenesis permitted identification of a new cis-regulatory element in the promoter region of the pcl1+ gene. This cis-acting regulatory sequence containing the pentanucleotide sequence CCAAT is responsible for transcriptional repress ...[more]

PMID: 16963626

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Project description:BackgroundHIV-1 protease (PR) is an essential viral enzyme. Its primary function is to proteolyze the viral Gag-Pol polyprotein for production of viral enzymes and structural proteins and for maturation of infectious viral particles. Increasing evidence suggests that PR cleaves host cellular proteins. However, the nature of PR-host cellular protein interactions is elusive. This study aimed to develop a fission yeast (Schizosaccharomyces pombe) model system and to examine the possible interaction of HIV-1 PR with cellular proteins and its potential impact on cell proliferation and viability.ResultsA fission yeast strain RE294 was created that carried a single integrated copy of the PR gene in its chromosome. The PR gene was expressed using an inducible nmt1 promoter so that PR-specific effects could be measured. HIV-1 PR from this system cleaved the same indigenous viral p6/MA protein substrate as it does in natural HIV-1 infections. HIV-1 PR expression in fission yeast cells prevented cell proliferation and induced cellular oxidative stress and changes in mitochondrial morphology that led to cell death. Both these PR activities can be prevented by a PR-specific enzymatic inhibitor, indinavir, suggesting that PR-mediated proteolytic activities and cytotoxic effects resulted from enzymatic activities of HIV-1 PR. Through genome-wide screening, a serine/threonine kinase, Hhp2, was identified that suppresses HIV-1 PR-induced protease cleavage and cell death in fission yeast and in mammalian cells, where it prevented PR-induced apoptosis and cleavage of caspase-3 and caspase-8.ConclusionsThis is the first report to show that HIV-1 protease is functional as an enzyme in fission yeast, and that it behaves in a similar manner as it does in HIV-1 infection. HIV-1 PR-induced cell death in fission yeast could potentially be used as an endpoint for mechanistic studies, and this system could be used for developing a high-throughput system for drug screenings.

Dataset Information

A transcription factor cascade involving Fep1 and the CCAAT-binding factor Php4 regulates gene expression in response to iron deficiency in the fission yeast Schizosaccharomyces pombe.

Publications

A transcription factor cascade involving Fep1 and the CCAAT-binding factor Php4 regulates gene expression in response to iron deficiency in the fission yeast Schizosaccharomyces pombe.

Similar Datasets

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