text: CTCF physically binds to itself to form homodimers,
  which causes the bound DNA to form loops. CTCF also occurs frequently at the boundaries of sections of DNA bound to the nuclear lamina. Using chromatin immuno-precipitation (ChIP) followed by ChIP-seq, it was found that CTCF localizes with cohesin genome-wide and affects gene regulatory mechanisms and the higher-order chromatin structure. It is currently believed that the DNA loops are formed by the "loop extrusion" mechanism, whereby the cohesin ring is actively being translocated along the DNA until it meets CTCF. CTCF has to be in a proper orientation to stop cohesin.