Altered Dosage and Mis-localization of Histone H3 and Cse4p Lead to Chromosome Loss in Saccharomyces cerevisiae
Wei-Chun Au 1, Matthew J Crisp 1, Steven Z DeLuca 1, Oliver J Rando 2 and Munira A Basrai 1*
1 National Cancer Institute
2 University of Massachusetts Medical School
* To whom correspondence should be addressed. E-mail: basraim{at}nih.gov.
Submitted on February 25, 2008
Revised on March 11, 2008
Accepted on 11 March 2008
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Abstract |
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Cse4p is an essential histone H3 variant in Saccharomyces cerevisiae that defines centromere identity and is required for proper segregation of chromosomes. In this study, we investigated phenotypic consequences of Cse4p mis-localization and increased dosage of histone H3 and Cse4p, and established a direct link between histone stoichiometry, mis-localization of Cse4p, and chromosome segregation. Overexpression of the stable Cse4p mutant, cse4K16R, resulted in its mis-localization, increased association with chromatin, and a high rate of chromosome loss, all of which were suppressed by constitutive expression of histone H3 (16H3). We determined that 16H3 did not lead to increased chromosome loss; however, increasing the dosage of histone H3 (GALH3) resulted in significant chromosome loss due to reduced levels of CEN-associated Cse4p and synthetic dosage lethality (SDL) in kinetochore mutants. These phenotypes were suppressed by GALCSE4. We conclude that the chromosome mis-segregation of GALcse4K16R and GALH3 strains are due to mis-localization and a functionally compromised kinetochore, respectively. Suppression of these phenotypes by histone 16H3 and GALCSE4 supports the conclusion that proper stoichiometry affects the localization of histone H3 and Cse4p, and is thus essential for accurate chromosome segregation.
Key Words:
Centromere identity, Chromosome segregation, Cse4, histones, kinetochore
