Myb-related Schizosaccharomyces pombe cdc5p is structurally and functionally conserved in eukaryotes

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• The Myb-related protein Cdc5p in Schizosaccharomyces pombe is vital for G2/M cell cycle progression.
• Understanding the evolutionary conservation of Cdc5 is key to elucidating its fundamental roles.

Purpose of the Study:

• To investigate the structural and functional conservation of Cdc5 proteins across diverse species.
• To explore the role of Myb repeats in Cdc5 function and identify potential novel regulatory pathways.

Main Methods:

• Isolation of Cdc5-related genes and cDNAs from Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, and Homo sapiens.
• Functional complementation assays using S. pombe cdc5-120 mutant.
• Site-directed mutagenesis of S. cerevisiae CEF1 (Cef1p) Myb repeats.
• Analysis of transcriptional activation of G2/M-regulated genes.

Main Results:

• Cdc5 cDNAs from humans and flies functionally complemented the S. pombe cdc5-120 mutant.
• S. cerevisiae CEF1 is essential for G2/M progression.
• Myb repeats of Cdc5p and Cef1p are important for in vivo function, though structural requirements differ from c-Myb.
• Multiple mutations in Cef1p's Myb repeats were needed for inactivation, and Cef1p does not activate SWI5 transcription.

Conclusions:

• Cdc5 family members are functionally conserved across evolution, playing essential roles in G2/M progression.
• The Myb repeats of Cdc5 proteins are critical for function, but exhibit distinct structural-functional relationships compared to c-Myb.
• Cdc5 proteins likely operate through a novel pathway to regulate the G2/M transition, independent of direct transcriptional activation of certain G2/M genes.