(A) Immunoblotting of lysates from 293H cells transfected with vector (empty vector) or plasmids encoding BRAF V600E-FLAG or PAPSS1-BRAF-FLAG demonstrate that the BRAF fusion activates MAPK pathway signaling similarly to BRAF V600E. (B) While MAPK pathway signaling induced by expression of BRAF V600E is sensitive to increasing doses (0, 0.1, 0.5, 1, and 5 μmol/L) of the BRAF inhibitor vemurafenib (vem) or the MEK inhibitor trametinib (tra), signaling induced by PAPSS1-BRAF is more sensitive to trametinib than vemurafenib. kDa, kilodalton.