MAP3K13 and melanoma: To assess whether the V600E mutant allele of BRAF was required for MEK phosphorylation by the MLKs in melanoma cells, we depleted A375 cells of BRAF using small interfering RNA (siRNA) and observed that MLK1–4 induction was still able to activate the MEK/ERK pathway, indicating that the BRAFV600E allele is dispensable for MLK-mediated activation of MEK in these cells (Fig. 3d).