• Title/Summary/Keyword: homothallic mating loci

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The 80th Threonine Residue of Histone H3 Is Important for Maintaining HM Silencing in Saccharomyces cerevisiae

  • Soojin Yeom;Junsoo Oh;Donghyun Kim;Jung-Shin Lee
    • Journal of Microbiology and Biotechnology
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    • v.34 no.1
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    • pp.39-46
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    • 2024
  • Gene expression in eukaryotic cells is intricately regulated by chromatin structure and various factors, including histone proteins. In Saccharomyces cerevisiae, transcriptionally silenced regions, such as telomeres and homothallic mating (HM) loci, are essential for genome stability and proper cellular function. We firstly observed the defective HM silencing in alanine substitution mutant of 80th threonine residue of histone H3 (H3T80A). To identify which properties in the H3T80 residue are important for the HM silencing, we created several substitution mutants of H3T80 residue by considering the changed states of charge, polarity, and structural similarity. This study reveals that the structural similarity of the 80th position of H3 to the threonine residue, not the polarity and charges, is the most important thing for the transcriptional silencing in the HM loci.

Molecular Comparison of Mating Type Loci and Adjacent Chromosomal Regions from Self-fertile and Self-sterile Cochliobolus Species

  • Yun, Sung-Hwan;B. Gillian Turgeon;Turgeon
    • The Plant Pathology Journal
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    • v.15 no.3
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    • pp.131-136
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    • 1999
  • In fungi known as ascomycetes, ability to mate is controlled by a single mating type (MAT) locus with two dissimilar sequences called idiomorphs carrying genes encoding transcription factors that are unrelated to each other. Fungi requiring strains with different MAT genes to complete the sexual process are heterothallic (self-sterile); species in which as single strain is able to undergo sexual reproduction are homothallic (self-fertile). Previous analysis of sequences from several heterothallic and homothallic species of the ascomycete genus Cochliobolus showed that homothallics evolve from heterothallics and that each known Cochliobolus homothallic species arose independently, from a different heterothallic ancestral species. Here we report detailed comparative analyses of MAT sequences ad their flanking regions, and show that: (1) The level of MAT gene similarity is not correlated with reproductive life style; (2) MAT proteins from all Cochliobolus species are conserved within the transcription factor signature sequences; they are not conserved in the carboxy terminal half of MAT-1, or third of MAT-2, except in those from very closely related species; (3) A gene (ORF1) of unknown function, consistently found on the MAT flank, is more conserved than are the MAT genes themselves; (4) The intergenic sequences diverge sharply among species.

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