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.

• Authors: Alexandre Mercier, Benoit Pelletier, Simon Labbé
• Journal: Eukaryotic cell (Eukaryot Cell) Vol. 5 Issue 11 Pg. 1866-81 (Nov 2006) ISSN: 1535-9778 [Print] United States
• PMID: 16963626 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• CCAAT-Binding Factor
• Fep1 protein, S pombe
• GATA Transcription Factors
• Php4 protein, S pombe
• Protein Subunits
• RNA, Messenger
• Schizosaccharomyces pombe Proteins

Topics

• Base Sequence
• CCAAT-Binding Factor (genetics, metabolism)
• GATA Transcription Factors (genetics, metabolism)
• Gene Expression Regulation, Fungal
• Iron Deficiencies
• Molecular Sequence Data
• Promoter Regions, Genetic
• Protein Subunits (metabolism)
• RNA, Messenger (metabolism)
• Schizosaccharomyces (genetics, physiology)
• Schizosaccharomyces pombe Proteins (genetics, metabolism)
• Sequence Alignment
• Signal Transduction (physiology)
• Transcription, Genetic