title: Tracing the origin of the fungal α1 domain places its ancestor in the HMG-box superfamily: implication for fungal mating-type evolution.
abstract: BACKGROUND
  Fungal mating types in self-incompatible Pezizomycotina are specified by one of two alternate sequences occupying the same locus on corresponding chromosomes. One sequence is characterized by a gene encoding an HMG protein, while the hallmark of the other is a gene encoding a protein with an α1 domain showing similarity to the Matα1p protein of Saccharomyces cerevisiae. DNA-binding HMG proteins are ubiquitous and well characterized. In contrast, α1 domain proteins have limited distribution and their evolutionary origin is obscure, precluding a complete understanding of mating-type evolution in Ascomycota. Although much work has focused on the role of the S. cerevisiae Matα1p protein as a transcription factor, it has not yet been placed in any of the large families of sequence-specific DNA-binding proteins.
  
  
  RESULTS
  We present sequence comparisons, phylogenetic analyses, and in silico predictions of secondary and tertiary structures, which support our hypothesis that the α1 domain is related to the HMG domain. We have also characterized a new conserved motif in α1 proteins of Pezizomycotina. This motif is immediately adjacent to and downstream of the α1 domain and consists of a core sequence Y-[LMIF]-x(3)-G-[WL] embedded in a larger conserved motif.
  
  
  CONCLUSIONS
  Our data suggest that extant α1-box genes originated from an ancestral HMG gene, which confirms the current model of mating-type evolution within the fungal kingdom. We propose to incorporate α1 proteins in a new subclass of HMG proteins termed MATα_HMG.
authors.affiliation: Department of Plant Biology and Forest Genetics, Uppsala Biocenter, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
authors.forename: Tom
authors.initials: T
authors.lastname: Martin
authors.forename: Shun-Wen
authors.initials: SW
authors.lastname: Lu
authors.forename: Herman
authors.initials: H
authors.lastname: van Tilbeurgh
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Ripoll
authors.forename: Christina
authors.initials: C
authors.lastname: Dixelius
authors.forename: B Gillian
authors.initials: BG
authors.lastname: Turgeon
authors.forename: Robert
authors.initials: R
authors.lastname: Debuchy
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001203:Ascomycota / Q000235:genetics; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000737:chemistry*; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D010802:Phylogeny; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D012984:Software
chemical_list: D005656:Fungal Proteins