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Sgt1 is required for human kinetochore assembly
Peter Steensgaard1, Massimiliano Garrè, Ivan Muradore
1Department of Experimental Oncology, European Institute of Oncology, Via Ripamonti 435, 20141 Milan, Italy.
EMBO Reports
|May 11, 2004
Summary
Mammalian Sgt1 protein is essential for proper kinetochore assembly, crucial for chromosome alignment during cell division. Depleting Sgt1 disrupts the spindle assembly checkpoint and weakens chromosome segregation.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Sgt1 is a known protein involved in kinetochore assembly in yeast and has roles in signaling and pathogen resistance in other organisms.
- The function of Sgt1 in mammalian cells, particularly its role in cell division, was previously unknown.
Purpose of the Study:
- To investigate the function of mammalian Sgt1 in cell division.
- To determine Sgt1's role in kinetochore assembly and the spindle assembly checkpoint in human cells.
Main Methods:
- RNA interference (RNAi) was used to deplete Sgt1 in HeLa cells.
- Mitotic spindle and chromosome alignment were analyzed.
- Spindle checkpoint activation and kinetochore protein levels (Mad1, Mad2, BubR1, Hec1, CENP-E, CENP-F, CENP-I, CENP-C) were assessed.
Main Results:
- Sgt1 depletion caused significant alterations in the mitotic spindle and chromosome alignment problems.
- Cells lacking Sgt1 experienced mitotic delay due to spindle checkpoint activation.
- The spindle checkpoint response was weakened, correlating with reduced kinetochore levels of Mad1, Mad2, and BubR1.
- Kinetochore assembly was impaired, preventing the localization of several key proteins (Hec1, CENP-E, CENP-F, CENP-I) but not CENP-C.
Conclusions:
- Sgt1 is an essential protein for mammalian kinetochore assembly.
- Sgt1 is a critical factor in ensuring proper localization of proteins to mitotic kinetochores.
- These findings support a conserved kinetochore assembly pathway from yeast to humans.