Related Experiment Video
Updated: Jul 18, 2026
Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets
Published on: August 13, 2016
Rae1 interaction with NuMA is required for bipolar spindle formation
Richard W Wong1, Günter Blobel, Elias Coutavas
1Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10021, USA.
Abstract:
In eukaryotic cells, the faithful segregation of daughter chromosomes during cell division depends on formation of a microtubule (MT)-based bipolar spindle apparatus. The Nuclear Mitotic Apparatus protein (NuMA) is recruited from interphase nuclei to spindle MTs during mitosis. The carboxy terminal domain of NuMA binds MTs, allowing a NuMA dimer to function as a "divalent" crosslinker that bundles MTs. The messenger RNA export factor, Rae1, also binds to MTs. Lowering Rae1 or increasing NuMA levels in cells results in spindle abnormalities. We have identified a mitotic-specific interaction between Rae1 and NuMA and have explored the relationship between Rae1 and NuMA in spindle formation. We have mapped a specific binding site for Rae1 on NuMA that would convert a NuMA dimer to a "tetravalent" crosslinker of MTs. In mitosis, reducing Rae1 or increasing NuMA concentration would be expected to alter the valency of NuMA toward MTs; the "density" of NuMA-MT crosslinks in these conditions would be diminished, even though a threshold number of crosslinks sufficient to stabilize aberrant multipolar spindles may form. Consistent with this interpretation, we found that coupling NuMA overexpression to Rae1 overexpression or coupling Rae1 depletion to NuMA depletion prevented the formation of aberrant spindles. Likewise, we found that overexpression of the specific Rae1-binding domain of NuMA in HeLa cells led to aberrant spindle formation. These data point to the Rae1-NuMA interaction as a critical element for normal spindle formation in mitosis.
Insights
The Nuclear Mitotic Apparatus protein (NuMA) and Rae1 interaction is crucial for proper spindle formation during cell division. Altering their balance impacts microtubule crosslinking, potentially leading to abnormal cell division.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Faithful chromosome segregation in eukaryotic cells relies on a bipolar spindle apparatus.
- Nuclear Mitotic Apparatus protein (NuMA) and Rae1 are key proteins involved in spindle formation.
- NuMA and Rae1 bind to microtubules (MTs), influencing spindle structure.
Purpose of the Study:
- To investigate the relationship between NuMA and Rae1 in mitotic spindle formation.
- To identify the specific interaction between NuMA and Rae1 during mitosis.
- To understand how this interaction affects microtubule crosslinking and spindle stability.
Main Methods:
- Identifying a mitotic-specific interaction between Rae1 and NuMA.
- Mapping the Rae1-binding site on NuMA.
- Manipulating cellular levels of Rae1 and NuMA (overexpression and depletion).
- Overexpressing the Rae1-binding domain of NuMA in HeLa cells.
Main Results:
- A specific binding site for Rae1 on NuMA was identified, potentially converting NuMA from a divalent to a tetravalent crosslinker.
- Altering Rae1 or NuMA concentrations affects NuMA's microtubule crosslinking valency.
- Prevented aberrant spindle formation by coupling NuMA overexpression with Rae1 overexpression or Rae1 depletion with NuMA depletion.
- Overexpression of the Rae1-binding domain of NuMA induced aberrant spindle formation.
Conclusions:
- The interaction between Rae1 and NuMA is critical for normal mitotic spindle formation.
- The balance of Rae1 and NuMA influences microtubule crosslinking density and spindle stability.
- Dysregulation of the Rae1-NuMA interaction leads to abnormal spindle formation and potential chromosome segregation errors.
Related Concept Videos
02:50Spindle Assembly
In most cells, centrosomes are the primary microtubule nucleation centers. In the centrosome-mediated pathway, the G2-prophase transition triggers centrosome maturation and increased microtubule nucleation. Progressive nucleation results in a microtubule array...
02:19The Spindle Assembly Checkpoint
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
02:11Forces Acting on Chromosomes
Microtubules and motor proteins exert two types of forces on...
02:57Attachment of Sister Chromatids
02:27The Mitotic Spindle
The bipolar configuration of the mitotic spindle facilitates chromosomal segregation, preparing the cell for division. One mechanism that ensures bipolar mitotic...
02:27The Mitotic Spindle
The bipolar configuration of the mitotic spindle facilitates chromosomal segregation, preparing the cell for division. One mechanism that ensures bipolar mitotic...