title: Histone deacetylase complexes promote trinucleotide repeat expansions.
abstract: Expansions of DNA trinucleotide repeats cause at least 17 inherited neurodegenerative diseases, such as Huntington's disease. Expansions can occur at frequencies approaching 100% in affected families and in transgenic mice, suggesting that specific cellular proteins actively promote (favor) expansions. The inference is that expansions arise due to the presence of these promoting proteins, not their absence, and that interfering with these proteins can suppress expansions. The goal of this study was to identify novel factors that promote expansions. We discovered that specific histone deacetylase complexes (HDACs) promote CTG•CAG repeat expansions in budding yeast and human cells. Mutation or inhibition of yeast Rpd3L or Hda1 suppressed up to 90% of expansions. In cultured human astrocytes, expansions were suppressed by 75% upon inhibition or knockdown of HDAC3, whereas siRNA against the histone acetyltransferases CBP/p300 stimulated expansions. Genetic and molecular analysis both indicated that HDACs act at a distance from the triplet repeat to promote expansions. Expansion assays with nuclease mutants indicated that Sae2 is one of the relevant factors regulated by Rpd3L and Hda1. The causal relationship between HDACs and expansions indicates that HDACs can promote mutagenesis at some DNA sequences. This relationship further implies that HDAC3 inhibitors being tested for relief of expansion-associated gene silencing may also suppress somatic expansions that contribute to disease progression.
authors.affiliation: Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland.
authors.forename: Kim
authors.initials: K
authors.lastname: Debacker
authors.forename: Aisling
authors.initials: A
authors.lastname: Frizzell
authors.forename: Olive
authors.initials: O
authors.lastname: Gleeson
authors.forename: Lucy
authors.initials: L
authors.lastname: Kirkham-McCarthy
authors.forename: Tony
authors.initials: T
authors.lastname: Mertz
authors.forename: Robert S
authors.initials: RS
authors.lastname: Lahue
mesh_terms: D001253:Astrocytes / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D004720:Endonucleases / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006655:Histone Deacetylases / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D009154:Mutation / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D004718:Saccharomycetales / Q000235:genetics*; D019680:Trinucleotide Repeat Expansion / Q000187:drug effects / Q000235:genetics*; D050880:p300-CBP Transcription Factors / Q000378:metabolism; D000099224:p300-CBP-Associated Factor
chemical_list: D004720:Endonucleases; D006655:Histone Deacetylases; D034741:RNA, Small Interfering; D029701:Saccharomyces cerevisiae Proteins; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C107849:SAE2 protein, S cerevisiae