Figure 1

(A) More recent findings imply that there are in fact several different classes of chromatin entry sites with varying affinity towards the DCC. (B1) When only the core proteins MSL1 and MSL2 are present, they are merely capable of weakly interacting with each other and gathering around the ~35 sites that have been denoted as high-affinity entry sites. (B2) The addition of MLE and one of the two roX RNAs amplifies this interaction, but only the fully assembled complex (B3) can spread along the entire X chromosome by interacting with the rest of the entry sites in normal concentrations.