Fusions with histone H3 result in highly specific alteration of gene expression.
Hap1 is a yeast transcriptional activator which controls expression of genes such as CYC1 and CYC7. Our results show that Hap1 activity is dependent on a functional chromatin remodeling complex SWI/SNF. Using a modified two-hybrid screen with Hap1 as bait, we recovered expression vectors encoding the Gal4 activation domain fused to histone H3 [Gal4(AD)-H3]. Hap1 activity at CYC1 or CYC7 was increased by Gal4(AD)-H3 and the effect was dependent on the presence of the activation domain of Hap1 and a functional SWI complex. Importantly, overexpression of H3 alone had no effect on Hap1 activity. Analysis of Gal4(AD)-H3 revealed that the fusion is not incorporated into the nucleosome while a functional Gal4 activation domain is dispensable. Activity of many other transcriptional activators was unchanged or slightly affected in the presence of Gal4(AD)-H3. Thus, our results identify a new class of histone H3 variants that cause highly specific alteration of gene expression. Hap1 may interact directly with H3 favoring chromatin remodeling by the SWI/SNF complex.
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Department of Medicine, Royal Victoria Hospital, Montréal, Québec, Canada.
Hellauer
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Turcotte
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D000595:Amino Acid Sequence; D019677:Artificial Gene Fusion; D001483:Base Sequence; D019757:Carbon-Oxygen Lyases / Q000502:physiology*; D017931:DNA Primers; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D006657:Histones / Q000235:genetics*; D015534:Trans-Activators / Q000502:physiology*
D017931:DNA Primers; D006657:Histones; D015534:Trans-Activators; D019757:Carbon-Oxygen Lyases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase