In melanoma and TC, unidentified importin and CRM1 shuttle RAF proteins (particularly BRAF) into and out of the nucleus, which phosphorylate MAPK/ERK kinases (MEKs) within the mitogen-activated protein kinase (MAPK) cascade upon activation by proto-oncogenes Rat sarcoma (RAS) proteins [46]. The gene discussed is RAF1; the disease is melanoma.