A histone-H3-like protein in C. elegans

The segregation of a chromosome during mitosis is mediated by a region of the chromosome known as the centromere, which organizes the kinetochore, to which the spindle microtubules attach. Many organisms have monocentric chromosomes, in which the centromeres map to single loci, whereas others, including the nematode Caenorhabditis elegans, have holocentric chromosomes, in which non-localized kinetochores extend along the length of each chromosome1,2. The centromeres of monocentric chromosomes use specialized nucleosomes containing histone-H3-like proteins (known as CENP-A in mammals3,4,5,6 and Cse4 in the yeast Saccharomyces cerevisiae7,8). Here we show that a C. elegans histone-H3-like protein is necessary for the proper segregation of chromosomes during mitosis and identifies the centromeres of these holocentric chromosomes, indicating that both holocentric and monocentric chromosomes use centromeric histone-H3-like proteins.