Figure 2. A proposed model for the position effect in peri-centromeric tandem repeats.

The condensin subunit Cut3 and other unknown upstream factors recruit key silencing effectors, such as RITS complex, to pericentromeric repeat arrays, and mediate the level of the silencing at individual repeats, leading to the position-dependent silencing. The less silenced repeats may generate siRNAs that in turn facilitate heterochromatin assembly in other repeats in trans. Position effects in pericentromeric repeat arrays indicates that these repeats are organized into distinct three-dimensional higher-order structure; such spatial arrangement helps to define and position the CENP-A^cnp1 enriched centromere core regions.