 In addition to phosphorylating MEK, A-Raf also inhibits MST2, a tumor suppressor and proapoptotic kinase not found in the MAPK pathway.By inhibiting MST2, A-Raf can prevent apoptosis from occurring.However, this inhibition is only possible when the splice factor heterogenous nuclear ribonucleoprotein H (hnRNP H) maintains the expression of a full-length A-Raf protein.