Kar4 is Required for the Normal Pattern of Meiotic Gene Expression

Area of Science:

• Molecular Biology
• Yeast Genetics
• Meiosis Regulation

Background:

• Kar4p, a yeast homolog of METTL14, is crucial for initiating meiosis.
• Kar4p exhibits dual functions, impacting both transcriptional and translational processes during meiosis.
• Loss of Kar4p leads to mRNA methylation defects and arrests the meiotic program.

Approach:

• Utilized microarray analysis and RNA sequencing to assess transcriptional profiles in kar4Δ/Δ mutants.
• Employed mass spectrometry to analyze protein levels of meiotic recombination genes.
• Investigated the effects of overexpressing IME1 and RIM4 on meiotic progression and gene expression.

Key Points:

• kar4Δ/Δ mutants display delayed and reduced expression of early (Ime1p-dependent) and late (Ndt80p-dependent) meiotic genes.
• Overexpression of IME1 rescues early gene expression defects, while late gene defects require co-overexpression of IME1 and RIM4.
• Reduced protein levels for meiotic recombination factors in kar4Δ/Δ mutants are rescued by co-overexpression of IME1 and RIM4, suggesting a non-catalytic function of Kar4p.

Conclusions:

• Kar4p plays essential roles in both transcriptional regulation and translational control during yeast meiosis.
• The meiotic defects in kar4Δ/Δ mutants, particularly for later meiotic events, are linked to translational regulation independent of mRNA methylation.
• Co-overexpression of IME1 and RIM4 is necessary to fully restore sporulation in the absence of Kar4p.