title: Separation-of-function mutation in HPC2, a member of the HIR complex in S. cerevisiae, results in derepression of the histone genes but does not confer cryptic TATA phenotypes.
abstract: The HIR complex, which is comprised of the four proteins Hir1, Hir2, Hir3 and Hpc2, was first characterized as a repressor of three of the four histone gene loci in Saccharomyces cerevisiae. Using a bioinformatical approach, previous studies have identified a region of Hpc2 that is conserved in Schizosaccharomyces pombe and humans. Using a similar approach, we identified two additional domains, CDI and CDII, of the Hpc2 protein that are conserved among yeast species related to S. cerevisiae. We showed that the N terminal CDI domain (spanning amino acids 63-79) is dispensable for HIR complex assembly, but plays an essential role in the repression of the histone genes by recruiting the HIR complex to the HIR-dependent histone gene loci. The second conserved domain, CDII (spanning amino acids 452-480), is required for the stability of the Hpc2 protein itself as well as for the assembly of the HIR complex. In addition, we report a novel separation-of-function mutation within CDI of Hpc2, which causes derepression of the histone genes but does not confer other reported hir/hpc- phenotypes (such as Spt phenotypes, heterochromatin silencing defects and repression of cryptic promoters). This is the first direct demonstration that a separation-of-function mutation exists within the HIR complex.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS 66160, USA.
authors.forename: Nidhi
authors.initials: N
authors.lastname: Vishnoi
authors.forename: Kacie
authors.initials: K
authors.lastname: Flaherty
authors.forename: Leandria C
authors.initials: LC
authors.lastname: Hancock
authors.forename: Monica E
authors.initials: ME
authors.lastname: Ferreira
authors.forename: Amit Dipak
authors.initials: AD
authors.lastname: Amin
authors.forename: Philippe
authors.initials: P
authors.lastname: Prochasson
mesh_terms: D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000235:genetics*; D002460:Cell Line; D015966:Gene Expression Regulation, Fungal; D005838:Genotype; D006657:Histones / Q000737:chemistry; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D010802:Phylogeny; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D018797:Cell Cycle Proteins; C077306:HPC2 protein, S cerevisiae; D006657:Histones; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors