Histone-histone interactions and centromere function.
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.
Glowczewski
L
L
Department of Microbiology and Cancer Center, University of Virginia, Charlottesville, Virginia 22908, USA.
Yang
P
P
Kalashnikova
T
T
Santisteban
M S
MS
Smith
M M
MM
D002503:Centromere / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D002843:Chromatin / Q000235:genetics / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D018628:Gene Dosage; D005804:Genes, Lethal; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D008941:Spindle Apparatus / Q000378:metabolism; D013489:Suppression, Genetic; D013696:Temperature
C092746:CSE4 protein, S cerevisiae; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D006657:Histones; D029701:Saccharomyces cerevisiae Proteins