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MEI4, a meiosis-specific yeast gene required for chromosome synapsis
T M Menees1, P B Ross-MacDonald, G S Roeder
1Department of Biology, Yale University, New Haven, Connecticut 06511-8112.
Abstract:
The MEI4 gene product is required for meiotic induction of recombination and viable spore production in the yeast Saccharomyces cerevisiae. DNA sequence analysis shows that the MEI4 gene encodes a 450-amino-acid protein bearing no homology to any previously identified protein. The MEI4 coding region is interrupted by a small intron located near the 5' end of the gene. Efficient splicing of the MEI4 transcript is not dependent on the MER1 protein, which is required for splicing the transcript of another meiotic gene, MER2. Expression of a mei4::lacZ fusion gene is meiosis-specific and depends on both heterozygosity at the mating-type locus and nutrient limitation. Northern (RNA) blot hybridization analysis suggests that MEI4 gene expression is regulated at the level of transcription. A functional MEI4 gene is not required for meiotic induction of transcription of the MER1, MER2, MEK1, RED1, SPO11, or RAD50 gene. Cytological analysis of mei4 mutant strains during meiotic prophase demonstrates that the chromosomes form long axial elements that fail to undergo synapsis. The meiosis II division is delayed in mei4 strains.
Insights
The MEI4 gene is crucial for yeast meiosis, enabling recombination and spore formation. Its absence disrupts chromosome synapsis and delays cell division, highlighting its essential role in sexual reproduction.
Area of Science:
- Molecular and Cellular Biology
- Genetics
- Yeast Research
Background:
- Meiosis is a fundamental process for sexual reproduction, involving genetic recombination and reductional cell division.
- Specific genes regulate meiotic progression, but the roles of some, like MEI4, remain incompletely understood.
- Understanding meiotic genes is vital for comprehending genome stability and reproductive success.
Purpose of the Study:
- To characterize the function of the MEI4 gene in Saccharomyces cerevisiae meiosis.
- To investigate the molecular mechanisms underlying MEI4's role in recombination and spore production.
- To determine the regulatory elements controlling MEI4 gene expression.
Main Methods:
- DNA sequence analysis to identify the MEI4 gene and its product.
- Gene fusion (mei4::lacZ) and Northern blot analysis to study gene expression.
- Cytological analysis of mei4 mutant strains during meiotic prophase.
Main Results:
- MEI4 encodes a novel 450-amino-acid protein essential for meiotic recombination and viable spore production.
- MEI4 expression is meiosis-specific, regulated transcriptionally, and dependent on mating-type heterozygosity and nutrient limitation.
- mei4 mutants exhibit defects in chromosome synapsis and delayed meiosis II division.
Conclusions:
- MEI4 is a novel, essential gene for meiotic progression in yeast.
- The MEI4 protein plays a critical role in chromosome structure and synapsis during meiotic prophase.
- MEI4 functions independently of MER1-mediated splicing and does not regulate the transcription of other known meiotic genes.