A melanoma-associated germline mutation in exon 1β inactivates p14ARF

The INK4a/ARF locus encodes the cyclin dependent kinase inhibitor, p16^INK4a and the p53 activator, p14ARF. These two proteins have an independent first exon (exon 1α and exon 1β, respectively) but share exons 2 and 3 and are translated in different reading frames. Germline mutations in this locus are associated with melanoma susceptibility in 20-40% of multiple case melanoma families. Although most of these mutations specifically inactivate p16^INK4a, more than 40% of the INK4a/ARF alterations located in exon 2, affect both p16^INK4a and p14ARF. We now report a 16 base pair exon 1β germline insertion specifically altering p14ARF, but not p16^INK4a, in an individual with multiple primary melanomas. This mutant p14ARF, 60ins16, was restricted to the cytoplasm, did not stabilize p53 and was unable to arrest the growth of a p53 expressing melanoma cell line. This is the first example of an exon 1β mutation that inactivates pl4ARF, and thus implicates a role for this turnout suppressor in melanoma predisposition.