Nup-PI: the nucleopore-promoter interaction of genes in yeast.

Our previous work identified the inner basket of the NPC as a physical activation/protection station for force-tethered, epigenetically silenced genes. Here we show that a specific nucleopore-to-gene-promoter interaction (Nup-PI) is an early physiological event of gene activation. Nup-PI was discovered with chromatin endogenous cleavage (ChEC) experiments that mapped in vivo the genomic interaction sites of the nucleoporin Nup2p fused to microccocal nuclease (Nup2-MN).

ChIC and ChEC; genomic mapping of chromatin proteins.

To map the genomic interaction sites of chromatin proteins, two related methods were developed and experimentally explored in Saccharomyces cerevisiae. The ChIC method (chromatin immunocleavage) consists of tethering a fusion protein (pA-MN) consisting of micrococcal nuclease (MN) and staphylococcal protein A to specifically bound antibodies. The nuclease is kept inactive during the tethering process (no Ca2+).