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Immunofluorescence Analysis of Endogenous and Exogenous Centromere-kinetochore Proteins
Published on: March 3, 2016
Structure and Scm3-mediated assembly of budding yeast centromeric nucleosomes
Mekonnen Lemma Dechassa1, Katharina Wyns, Ming Li
1Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, USA.
Nature Communications
|May 19, 2011
Summary
The yeast centromeric nucleosome, featuring Cse4 (a histone H3 variant), forms an open octameric structure. The protein Scm3 acts as an assembly factor but is not a stable component of the final centromeric nucleosome.
Area of Science:
- Molecular Biology
- Chromatin Biology
- Yeast Genetics
Background:
- The structural organization of yeast centromeric nucleosomes and the function of Scm3 remain debated.
- Understanding centromeric nucleosome structure is crucial for chromosome segregation.
Purpose of the Study:
- To elucidate the structural organization of yeast centromeric nucleosomes.
- To define the role of the nonhistone protein Scm3 in centromeric nucleosome assembly and architecture.
Main Methods:
- Single-molecule biophysical approaches.
- Micrococcal nuclease digestion assays.
- Small-angle X-ray scattering (SAXS).
Main Results:
- Substitution of histone H3 with its centromeric variant Cse4 yields octameric nucleosomes with DNA organized in a left-handed superhelix.
- Cse4-nucleosomes display an open conformation with loosely associated terminal DNA segments.
- Cse4-octamers do not exhibit preferential binding to centromeric DNA.
- Scm3 functions as a specific assembly factor for Cse4-nucleosomes, but is not stably incorporated.
Conclusions:
- The budding yeast centromeric nucleosome is an open octameric structure involving Cse4.
- Scm3 is essential for Cse4-nucleosome formation but is transiently associated.
- These findings clarify the assembly pathway and structural characteristics of yeast centromeric nucleosomes.
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