The IFH1 gene product interacts with a fork head protein in Saccharomyces cerevisiae.
FHL1 encodes a polypeptide closely related to the fork head protein family of transcriptional activators. Deleting this gene leads to a slow-growth phenotype with impaired rRNA maturation. IFH1 (located on chromosome IV) was isolated as a dosage-dependent suppressor partially correcting the growth defect of the fhl1 deletion. It codes for a highly hydrophilic protein with a predicted molecular weight of 122 kDa and a pI of 4.8, that is very rich in charged residues (mostly acidic) but otherwise unrelated to any known protein. Carboxy-terminal deletions removing the last third of the protein lead to a leaky growth phenotype with impaired rRNA maturation, as in the case of the fhl1 deletion. A full deletion of IFH1 is lethal, but growth was restored in a strain deleted for both IFH1 and FHL1. Thus, Ifh1p is essential for growth, but only in the presence of a functional Fhp1p protein. Conversely, its overexpression by increased gene dosage partially compensates for the genetic inactivation of Fhl1p. These data suggest a direct interaction between the Fhl1p and Ifh1p proteins, and are consistent with a model where Fhl1p is converted from a transcriptional repressor to an activator on binding of Ifh1p.
Cherel
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I
Service de Biochimie & Génétique Moléculaire, CEA (Saclay), Gif sur Yvette, France.
Thuriaux
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P
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D051858:Forkhead Transcription Factors; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D005800:Genes, Fungal; D008954:Models, Biological; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D012322:RNA Precursors / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012331:RNA, Fungal / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism*
D051858:Forkhead Transcription Factors; D005656:Fungal Proteins; C094046:IFH1 protein, S cerevisiae; D009687:Nuclear Proteins; D012322:RNA Precursors; D012331:RNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors