Vertebrate CTF18 and DDX11 essential function in cohesion is bypassed by preventing WAPL-mediated cohesin release

The alternative PCNA loader containing CTF18-DCC1-CTF8 facilitates sister chromatid cohesion (SCC) by poorly defined mechanisms. Here we found that in DT40 cells, CTF18 acts complementarily with the Warsaw breakage syndrome DDX11 helicase in mediating SCC and proliferation. We uncover that the lethality and cohesion defects of mutants are associated with reduced levels of chromatin-bound cohesin and rescued by depletion of WAPL, a cohesin-removal factor. On the contrary, high levels of acetyltransferases that acetylate cohesin to establish SCC do not rescue phenotypes. Notably, the tight proximity of sister centromeres and increased anaphase bridges characteristic of WAPL-depleted cells are abrogated by loss of both and The results reveal that vertebrate CTF18 and DDX11 collaborate to provide sufficient amounts of chromatin-loaded cohesin available for SCC generation in the presence of WAPL-mediated cohesin-unloading activity. This process modulates chromosome structure and is essential for cellular proliferation in vertebrates.