Transactivation by Rtg1p, a basic helix-loop-helix protein that functions in communication between mitochondria and the nucleus in yeast

J Biol Chem. 1995 Dec 8;270(49):29476-82. doi: 10.1074/jbc.270.49.29476.

Abstract

Rtg1p is a basic helix-loop-helix transcription factor in the yeast Saccharomyces cerevisiae that is required for basal and regulated expression of CIT2, the gene encoding a peroxisomal isoform of citrate synthase. In respiratory incompetent rho degree petite cells, CIT2 transcription is elevated as much as 30-fold compared with respiratory competent rho + cells. Here we provide evidence that Rtg1p interacts directly with a CIT2 upstream activation site (UASr) and that the rho degree/rho + regulation is not due to a change in the levels of Rtg1p. A fusion protein consisting of the DNA binding domain of Gal4p fused to the NH2 terminus of the full-length wild-type Rtg1p was able to transactivate an integrated LacZ reporter under control of the Gal4p-responsive GAL1 UASG in a rho degree/rho(+)-dependent manner. Other Gal4p fusions to deletions or mutations of Rtg1p indicate that the helix-loop-helix domain is essential for transactivation. Regulated expression of CIT2 also requires the RTG2 gene product. The Gal4-Rtg1p fusion was unable to transactivate the LacZ reporter gene in a strain deleted for RTG2, suggesting that the RTG2 product does not act independently of Rtg1p in the rho degree/rho + transcriptional response.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alleles
  • Base Sequence
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
  • Cell Nucleus / physiology
  • Citrate (si)-Synthase / genetics
  • DNA / metabolism
  • Fungal Proteins / genetics
  • Fungal Proteins / physiology*
  • Genes, Reporter
  • Helix-Loop-Helix Motifs*
  • Intracellular Signaling Peptides and Proteins
  • Mitochondria / physiology
  • Molecular Sequence Data
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae Proteins*
  • Trans-Activators / physiology*
  • Transcription Factors*

Substances

  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
  • Fungal Proteins
  • Intracellular Signaling Peptides and Proteins
  • RTG1 protein, S cerevisiae
  • RTG2 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Trans-Activators
  • Transcription Factors
  • DNA
  • Citrate (si)-Synthase