POLR3A and melanoma: To confirm the observed effect of BRAFV600E inhibition on URI1 interaction with RNA polymerases, we performed URI1 co-immunoprecipitation experiments in a panel of BRAFV600E-mutated melanoma cell lines (A375-P, A2058, SK-MEL-28 and UACC-62) treated with PLX4720 for 24 h and blotted for each of the large subunits of the three nuclear RNA polymerases POLR1A, POLR2A and POLR3A [polymerase RNA (I, II, III) DNA-directed polypeptide A].