title: Identification of RTG2 as a modifier gene for CTG*CAG repeat instability in Saccharomyces cerevisiae.
abstract: Trinucleotide repeats (TNRs) undergo frequent mutations in families affected by TNR diseases and in model organisms. Much of the instability is conferred in cis by the sequence and length of the triplet tract. Trans-acting factors also modulate TNR instability risk, on the basis of such evidence as parent-of-origin effects. To help identify trans-acting modifiers, a screen was performed to find yeast mutants with altered CTG.CAG repeat mutation frequencies. The RTG2 gene was identified as one such modifier. In rtg2 mutants, expansions of CTG.CAG repeats show a modest increase in rate, depending on the starting tract length. Surprisingly, contractions were suppressed in an rtg2 background. This creates a situation in a model system where expansions outnumber contractions, as in humans. The rtg2 phenotype was apparently specific for CTG.CAG repeat instability, since no changes in mutation rate were observed for dinucleotide repeats or at the CAN1 reporter gene. This feature sets rtg2 mutants apart from most other mutants that affect genetic stability both for TNRs and at other DNA sequences. It was also found that RTG2 acts independently of its normal partners RTG1 and RTG3, suggesting a novel function of RTG2 that helps modify CTG.CAG repeat mutation risk.
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha 68198-6805, USA.
authors.forename: Saumitri
authors.initials: S
authors.lastname: Bhattacharyya
authors.forename: Michael L
authors.initials: ML
authors.lastname: Rolfsmeier
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dixon
authors.forename: Kara
authors.initials: K
authors.lastname: Wagoner
authors.forename: Robert S
authors.initials: RS
authors.lastname: Lahue
mesh_terms: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D047908:Intracellular Signaling Peptides and Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D018911:Trinucleotide Repeats / Q000502:physiology*
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D047908:Intracellular Signaling Peptides and Proteins; C079378:RTG1 protein, S cerevisiae; C079379:RTG2 protein, S cerevisiae; C104438:RTG3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors