An enzymatic-independent function of palmitoyl hydrolase in cohesin loading onto chromosome.

Sister chromatid cohesion is mediated by a conserved multiprotein complex called cohesin. The loading of cohesin onto chromosomes involves the RSC (remodels the structure of chromatin) chromatin remodeling complex. Here, we demonstrate that the fission yeast Phi1, a palmitoyl hydrolase inactive protein 1, serves to bridge the interaction between cohesin and the RSC complex. Phi1 interacts with Rad21 in cohesin and Snf21, the RSC complex ATPase, to promote chromosome loading of cohesin. The identified characteristic features of Phi1 are conserved in the human homologues Apt1 and Apt2, which interact with Rad21 and Brg1, the human homologue of Snf21, in an enzymatic-independent manner. Intriguingly, the cohesin-Apt1-Brg1 complex is upregulated in C4-2B prostate cancer cells, and co-depletion of Apt1 and Apt2 by small interfering RNA triggers mitotic catastrophe in these cells. In addition, Apt1 nuclear localization is associated with poor clinical outcomes in prostate cancer. These results suggest a pro-survival function against mitotic stress for the complex.