Slk19-dependent mid-anaphase pause in kinesin-5-mutated cells

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Kinesin-5 motor proteins are crucial for spindle assembly and function.
• Anaphase spindle elongation is a critical process for chromosome segregation.
• The FEAR pathway regulates early-anaphase events, including Cdc14 phosphatase activation.

Purpose of the Study:

• To investigate the role of kinesin-5 motor proteins (Cin8 and Kip1) in anaphase spindle elongation in Saccharomyces cerevisiae.
• To determine the impact of specific kinesin-5 mutations on spindle dynamics and midzone organization.
• To explore the involvement of FEAR pathway components and the pre-anaphase checkpoint in regulating spindle elongation defects.

Main Methods:

• Yeast genetics: construction of kip1 deletion and expression of Cin8 motor-domain mutants (Cin8-F467A, Cin8-R196K).
• Microscopy to observe anaphase spindle elongation and midzone structure.
• Genetic manipulation of FEAR pathway components (SLK19, SPO12) and Cdc20 to assess their effects.

Main Results:

• Kinesin-5 mutations, particularly in kip1 Delta cin8-F467A cells, led to interrupted spindle elongation and a mid-anaphase pause.
• Mutant cells exhibited asymmetric midzone location and enlarged midzone size, indicating impaired organization.
• Deletion of SLK19, but not SPO12, abolished the mid-anaphase pause, induced premature anaphase onset, and caused DNA division defects.
• Overexpression of Cdc20 also eliminated the pause but resulted in DNA deformation.

Conclusions:

• Proper kinesin-5 function and midzone organization are essential for continuous anaphase spindle elongation.
• A Slk19-dependent mid-anaphase pause, potentially triggered by pre-anaphase checkpoint activation in kinesin-5 mutants, may be vital for accurate DNA segregation.