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Molecular and Cellular Biology, August 2000, p. 5700-5711, Vol. 20, No. 15
Department of Microbiology and Cancer Center,
University of Virginia, Charlottesville, Virginia 22908
Received 22 February 2000/Returned for modification 18 April
2000/Accepted 26 May 2000
Cse4p is a structural component of the core centromere of
Saccharomyces cerevisiae and is a member of the conserved
CENP-A family of specialized histone H3 variants. The histone H4 allele hhf1-20 confers defects in core centromere chromatin
structure and mitotic chromosome transmission. We have proposed that
Cse4p and histone H4 interact through their respective histone fold domains to assemble a nucleosome-like structure at centromeric DNA. To
test this model, we targeted random mutations to the Cse4p histone fold
domain and isolated three temperature-sensitive cse4 alleles in an unbiased genetic screen. Two of the cse4
alleles contain mutations at the Cse4p-H4 interface. One of these
requires two widely separated mutations demonstrating long-range
cooperative interactions in the structure. The third cse4
allele is mutated at its helix 2-helix 3 interface, a region required
for homotypic H3 fold dimerization. Overexpression of wild-type Cse4p
and histone H4 confer reciprocal allele-specific suppression of
cse4 and hhf1 mutations, providing strong
evidence for Cse4p-H4 protein interaction. Overexpression of histone H3
is dosage lethal in cse4 mutants, suggesting that histone
H3 competes with Cse4p for histone H4 binding. However, the relative
resistance of the Cse4p-H4 pathway to H3 interference argues that
centromere chromatin assembly must be highly regulated.
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Histone-Histone Interactions and Centromere
Function
*
Corresponding author. Mailing address: Department of
Microbiology and Cancer Center, University of Virginia, 1300 Jefferson Park Ave., Charlottesville, VA 22908. Phone: (804) 924-2669. Fax: (804)
982-1071. E-mail: mms7r{at}virginia.edu.
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