Cohesin catalyzes folding of the genome into loops that are anchored by CTCF. In a great collaboration with the lab of Daniel Panne, we show that the interaction of the CTCF N-terminus with the SA2-SCC1 subunits of cohesin is essential for CTCF-anchored loops. This interaction stabilizes cohesin on chromatin, and contributes to the positioning of cohesin at CTCF binding sites. We propose that CTCF enables chromatin loop formation by protecting cohesin against loop release. Our results provide fundamental insights into the molecular mechanism that allows dynamic chromatin folding by cohesin and CTCF.