The mouse mitotic checkpoint gene bub1b, a novel bub1 family member, is expressed in a cell cycle-dependent manner

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• The mitotic checkpoint ensures accurate chromosome segregation during cell division.
• The yeast mitotic checkpoint protein Bub1 is crucial for this process.
• Previous research identified mouse Bub1a (mBub1a).

Purpose of the Study:

• To identify novel genes involved in the mitotic checkpoint.
• To characterize a newly discovered homolog of Bub1 in mice, termed mBub1b.
• To investigate the expression patterns and potential functions of mBub1a and mBub1b.

Main Methods:

• Differential gene expression analysis in mouse thymocytes.
• Sequence homology analysis.
• Northern blot analysis of gene expression in various tissues.
• Cell cycle synchronization and expression profiling.
• Human gene mapping.

Main Results:

• A novel mouse Bub1 homolog, mBub1b, was identified with 40% sequence similarity to mBub1a.
• mBub1b possesses a putative destruction box, suggesting a role in protein degradation during mitosis.
• Both mBub1a and mBub1b genes are expressed in thymus and spleen, but not in non-dividing tissues.
• Expression of both genes is cell cycle-dependent, peaking in G2/M, with mBub1b expression delayed relative to mBub1a.
• The human mBub1b gene was mapped to chromosome 15q15.

Conclusions:

• Mammals possess two distinct Bub1 genes, mBub1a and mBub1b, encoding separate proteins.
• The differential timing of peak expression suggests distinct roles for mBub1a and mBub1b in the mitotic checkpoint.
• These findings provide insights into the complex regulation of mitosis in mammalian cells.