Directional bias during mating type switching in Saccharomyces is independent of chromosomal architecture

Peter Simon, Peter Houston, James Broach

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Haploid Saccharomyces cells have the remarkable potential to change mating type as often as every generation, a process accomplished by an intra-chromosomal gene conversion between an expressor locus MAT and one of two repositories of mating type information, HML or HMR. The particular locus selected as donor is dictated by the mating type of the cell, a bias that ensures productive mating type inter-conversion. Here we use green fluorescent protein tagging of the expressor and donor loci on chromosome III to show that this preference for donor locus does not result from a predetermined organization of chromosome III: HML and MAT as well as HMR and MAT remain separated in cells of both mating types. In fact, cells in which the inappropriate donor locus is artificially tethered to MAT still predominantly select the correct donor. We find, though, that initiation of switching leads to a rapid association of the correct donor locus with MAT. Thus, in mating type switching in Saccharomyces, donor preference is imposed at commitment to recombination rather than at physical contact of interacting DNA strands.

Original languageEnglish (US)
Pages (from-to)2282-2291
Number of pages10
JournalEMBO Journal
Issue number9
StatePublished - May 1 2002

All Science Journal Classification (ASJC) codes

  • General Neuroscience
  • Molecular Biology
  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology


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