MACs assemble chromatin proteins (green) on CENP-B–containing alphoid sequences (red).
Centromeric chromatin assembles at AT-rich repeats called α satellite sequences, or alphoids. Type I alphoids contain boxes for the binding of CENP-B, one of several conserved protein components of centromeric chromatin. Alphoid sequences are also found in inactivated centromeres, and Y chromosomes form centromeric chromatin, although they lack CENP-B boxes. Thus, centromeres are thought to be inherited as a preassembled complex.
However, assembly of new centromeric chromatin (de novo formation) requires specific sequences, according to the new results. The authors transformed cells with synthetic type I alphoid DNA constructs and looked for the formation of mammalian artificial chromosomes (MACs), which by definition...
