title: Identification of a multifunctional domain in autonomously replicating sequence-binding factor 1 required for transcriptional activation, DNA replication, and gene silencing.
abstract: Autonomously replicating sequence-binding factor 1 (ABF1) is a multifunctional, site-specific DNA binding protein that is essential for cell viability in Saccharomyces cerevisiae. ABF1 plays a direct role in transcriptional activation, stimulation of DNA replication, and gene silencing at the mating-type loci. Here we demonstrate that all three activities of ABF1 are conferred by the C terminus of the protein (amino acids [aa] 604 to 731). Furthermore, a detailed mutational analysis has revealed two important clusters of amino acid residues in the C terminus (C-terminal sequence 1 [CS1], aa 624 to 628; and CS2, aa 639 to 662). While both regions play a pivotal role in supporting cell viability, they make distinct contributions to ABF1 functions in various nuclear processes. CS1 specifically participates in transcriptional silencing and/or repression in a context-dependent manner, whereas CS2 is universally required for all three functions of ABF1. When tethered to specific regions of the genome, a 30-aa fragment that contains CS2 alone is sufficient for activation of transcription and chromosomal replication. In addition, CS2 is responsible for ABF1-mediated chromatin remodeling. Based on these results, we suggest that ABF1 may function as a chromatin-reorganizing factor to increase accessibility of the local chromatin structure, which in turn facilitates the action of additional factors to establish either an active or repressed chromatin state.
authors.affiliation: Department of Biochemistry and Molecular Genetics, School of Medicine, University of Virginia, Charlottesville, Virginia 22908-0733, USA.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Miyake
authors.forename: Christian M
authors.initials: CM
authors.lastname: Loch
authors.forename: Rong
authors.initials: R
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D002843:Chromatin / Q000235:genetics; D015825:Chromosomes, Fungal / Q000235:genetics; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020868:Gene Silencing; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: C061886:ABF1 protein, S cerevisiae; D002843:Chromatin; D004268:DNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors