Leptomycin B

A potent and specific nuclear export inhibitor. Leptomycin B alkylates and inhibits CRM1/exportin 1, a protein required for nuclear export of proteins containing a nuclear export sequence (NES). In addition to antifungal and antibacterial activities, blocks the cell cycle and is a potent anti-tumor agent. At low nM concentrations, blocks the nuclear export of many proteins including HIV-1 Rev, MAPK/ERK, and NF-κB/IκB and it stabilizes the expression of p53. Other proteins that are influenced by leptomycin B are actin, c-Abl, cyclin B1, MDM2/p53, Iκb, MPF and PKA. Leptomycin B also inhibits the export and translation of many RNAs, including COX-2 and c-Fos mRNAs, by inhibiting export of ribonucleoproteins.