The sequence elements of Saccharomyces cerevisiae centromeres are not present in other eukaryotes; they are absent even in other yeast species. The DNA sequences of centromeres are highly diverse among eukaryotes. However, some similarities have been revealed in centromere consensus sequences among eukaryotes. The centromeres of multicellular eukaryotes are surrounded by highly repetitive DNA ; centromeres themselves contain tandem repeats. One of the centromere repeat sequences present in humans is called alphoid, also known as α-satellite DNA. It is about 170 nucleotides in length and is repeated many times in a tandem array in the centromere.
Alphoid sequences have a conserved sequence called the CENP-B box. It has the following consensus sequence:
PyTTCGTTGGAAPuCGGGA, where Py=pyrimidine and Pu=purine.
This sequence serves as a binding site for proteins associated with the centromere. The CENP-B box is also found in other mammals and in Drosophila. The CENP-B box may be a common sequence in the highly diverse centromeric sequences of multicellular eukaryotes.