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The budding yeast Msh4 protein functions in chromosome synapsis and the regulation of crossover distribution

J E Novak1, P B Ross-Macdonald, G S Roeder

  • 1Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA.

Genetics
|July 17, 2001
PubMed

Insights

The MSH4 gene is crucial for regulating crossing over during meiosis in yeast. Its absence disrupts crossover interference and synaptonemal complex formation, suggesting a key role in these meiotic processes.

Area of Science:

  • * Genetics
  • * Molecular Biology
  • * Cell Biology

Background:

  • * The MSH4 gene in budding yeast encodes a MutS homolog essential for meiotic crossing over.
  • * MSH4 is specifically produced in meiotic cells and is not involved in mismatch repair or gene conversion.
  • * A msh4 null mutation significantly reduces crossover interference and affects crossing over levels.

Purpose of the Study:

  • * To investigate the role of MSH4 in meiotic crossing over and interference.
  • * To determine the relationship between MSH4, synaptonemal complex (SC) formation, and crossover interference.
  • * To explore the localization of MSH4 and its interaction with other meiotic proteins like Zip2 and Zip1.

Main Methods:

  • * Gene deletion to create msh4 null mutants.
  • * Analysis of crossover interference and crossing over levels.
  • * Epistasis tests to determine genetic interactions between msh4 and other meiotic mutants (zip1, ndj1/tam1).
  • * Immunofluorescence microscopy to examine SC formation and protein localization (Msh4, Zip2, Zip1).

Main Results:

  • * Msh4 is required for wild-type levels of crossing over and normal crossover interference.
  • * msh4 mutants exhibit delayed SC formation and incomplete synapsis.
  • * Msh4 protein localizes to meiotic chromosomes and colocalizes with Zip2.
  • * Zip1 and Zip2 are necessary for proper Msh4 localization to chromosomes.

Conclusions:

  • * MSH4 plays a critical role in regulating meiotic crossing over and interference.
  • * The synaptonemal complex (SC) appears to mediate crossover interference, as suggested by defects in msh4, zip1, and ndj1/tam1 mutants.
  • * Defects in SC formation or associated proteins (Zip1, Zip2) may indirectly affect crossing over by disrupting Msh4 localization.

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