Mps1 phosphorylates Borealin to control Aurora B activity and chromosome alignment

Area of Science:

• Cell biology
• Molecular biology
• Genetics

Background:

• Chromosomal stability is crucial for cell division and relies on accurate chromosome segregation during mitosis.
• The mitotic checkpoint ensures proper chromosome attachment to the spindle, preventing aneuploidy.
• Improper chromosome attachments must be corrected to maintain genomic integrity.

Purpose of the Study:

• To investigate the role of Monopolar spindle 1 (Mps1) kinase in correcting improper chromosome attachments.
• To elucidate the mechanism by which Mps1 regulates Aurora B kinase activity at centromeres.
• To understand how Mps1 coordinates checkpoint signaling and attachment error correction.

Main Methods:

• Phosphorylation assays to determine Mps1 targets.
• Analysis of chromosome alignment and attachment in Mps1-depleted cells.
• Site-directed mutagenesis to create phosphomimetic Borealin/DasraB mutants.

Main Results:

• Mps1 directly phosphorylates Borealin/DasraB, a regulator of Aurora B kinase.
• Mps1 activity is essential for Aurora B function at centromeres and efficient chromosome alignment.
• Loss of Mps1 kinase activity leads to uncorrected improper chromosome attachments.
• Phosphomimetic Borealin/DasraB mutants rescue chromosome alignment defects in Mps1-depleted cells.

Conclusions:

• Mps1 kinase plays a dual role in mitosis, regulating both the mitotic checkpoint and attachment error correction.
• Mps1 coordinates these processes by phosphorylating Borealin/DasraB, thereby controlling Aurora B activity.
• This mechanism ensures proper chromosome segregation and maintains chromosomal stability.