This model integrates current data. The DCC binds to rex sites in a sequence-dependent manner requiring SDC-2, SDC-3, and DPY-30. rex sites confer X-specificity to DCC binding and recruit additional complexes to bind along X at dox sites, which are unable to recruit the DCC when detached from X. Many dox sites on X have a small, intrinsic DCC binding capability; this binding is enhanced in response to DCC loading onto rex sites. dox sites are located preferentially in promoters of active genes, and positions of dox sites change as gene expression changes, implying that dox-site binding is transcription dependent.