The IFH1 gene product interacts with a fork head protein in Saccharomyces cerevisiae

Yeast. 1995 Mar;11(3):261-70. doi: 10.1002/yea.320110308.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Cloning, Molecular
  • Forkhead Transcription Factors
  • Fungal Proteins / genetics*
  • Fungal Proteins / metabolism*
  • Gene Deletion
  • Genes, Fungal
  • Models, Biological
  • Molecular Sequence Data
  • Nuclear Proteins / metabolism*
  • Phenotype
  • Plasmids / genetics
  • RNA Precursors / metabolism
  • RNA Processing, Post-Transcriptional
  • RNA, Fungal / metabolism
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins*
  • Trans-Activators*
  • Transcription Factors / metabolism*


  • Forkhead Transcription Factors
  • Fungal Proteins
  • IFH1 protein, S cerevisiae
  • Nuclear Proteins
  • RNA Precursors
  • RNA, Fungal
  • Saccharomyces cerevisiae Proteins
  • Trans-Activators
  • Transcription Factors

Associated data

  • GENBANK/Z29488