The Dictyostelium centromeric histone H3 variant. (A) Dictyostelium H3a and DdCenH3 (H3v1) are highlighted in orange on the left. Below the alignment is a schematic presentation of the domain organization of histone H3, with the N-terminal α-helix (αN), α-helixes 1–3 (α1–3) and loops 1 and 2 (L1, L2) indicated. L1 and α2, which have been shown to be responsible for targeting of CenH3 to centromeres are shaded green. Hs, Homo sapiens; At, Arabidopsis thaliana; Dd, Dictyostelium discodeum; Eh, Entamoeba histolytica; Sc, Saccharomyces cerevisiae; Xl, Xenopus laevis; Ce, Caenorhabditis elegans; Dt, Drosophila teissieri; Gi, Giardia intestinalis. (B) The organization of the centromeres was examined in fixed cells expressing GFP-DdCenH3 and immunostained with the centrosome marker DdCP224 at the indicated stages of the cell cycle. (C) Prophase of a diploid cell immunostained with DdCP224 and expressing GFP-DdCenH3 displays up to 12 GFP-DdCenH3 labelled foci presumably corresponding to the 12 centromeres. Scale bar = 1 µm.