Figure 1.

Schematic of centromere structure in fission yeast,D. melanogaster, and humans. Fission yeast centromere contains a central core region (cnt), flanked by imr and otr repeat regions. Each of the otr repeats can be divided into 2 smaller repeat units: dg (blue color) and dh (orange color). imr and otr repeat regions are heterochromatic. The sequence and size of DNA repeats in D. melanogaster and human centromeres are different from those in fission yeast (Schueler et al., 2001; Sun et al., 2003), but the general chromatin structure and epigenetic profile are conserved among these organisms. At core centromeres, the histone H3 variant, CENP-A, replaces histone H3 in nucleosomes, while histone H3K9 methylation is enriched at the peri-centromeric heterochromatin