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Mating type-dependent constraints on the mobility of the left arm of yeast chromosome III

Debra A Bressan1, Julio Vazquez, James E Haber

  • 1Rosenstiel Center and Department of Biology, Brandeis University, Waltham, MA 02454-9910, USA.

The Journal of Cell Biology
|January 28, 2004
PubMed

Insights

Budding yeast mating-type switching shows donor preference. The recombination enhancer (RE) controls HML tethering, which is relieved in MATa cells, influencing chromosome pairing during recombination.

Area of Science:

  • Cellular and Molecular Biology
  • Genetics
  • Yeast Biology

Background:

  • Mating-type gene (MAT) switching in budding yeast involves preferential recombination with specific donor loci (HML or HMR).
  • Donor preference is regulated by a recombination enhancer (RE) near HML, but the physical constraints governing this process are not fully understood.

Purpose of the Study:

  • To investigate the role of the recombination enhancer (RE) in controlling the physical positioning and mobility of the HML locus during mating-type switching.
  • To determine if HML pairing with MATalpha is constrained and how this relates to the mating-type locus and RE activity.

Main Methods:

  • Utilized live-cell imaging of LacI-GFP-bound lactose operator (lacO) arrays inserted at various chromosomal locations in budding yeast.
  • Assessed the mobility and constraint of chromosomal loci, including HML, in different mating-type strains (MATa, MATalpha) and with modifications to the recombination enhancer (RE).

Main Results:

  • HML locus mobility is significantly constrained in MATalpha and RE-deleted MATa strains, indicating mating-type-dependent tethering.
  • This constraint is relieved in MATa cells with an intact RE, suggesting RE actively modulates HML positioning.
  • Chromosome movement at HMR and other telomeric regions is independent of mating type.

Conclusions:

  • HML locus exhibits constitutive tethering, which is actively released in MATa cells by the action of the recombination enhancer (RE).
  • The three-dimensional organization of MAT, HML, and HMR loci is mating-type dependent, influencing donor preference.
  • These findings reveal a mechanism for regulating chromosomal interactions critical for mating-type gene switching.

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