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

The INK4a/ARF locus encodes the cyclin dependent kinase inhibitor, p16(INK4 a) and the p53 activator, p14ARF. These two proteins have an independent fi rst exon (exon 1 alpha and exon 1 beta, respectively) but share exons 2 and 3 and are translated in different reading frames. Germline mutations in th is locus are associated with melanoma susceptibility in 20-40% of multiple case melanoma families. Although most of these mutations specifically inact ivate p16(INK4a), more than 40% of the INK4a/ARF alterations located in exo n 2, affect both p16(INK4a) and p14ARF. We now report a 16 base pair exon 1 beta germline insertion specifically altering p14ARF, but not p16(INK4a), in an individual with multiple primary melanomas. This mutant p14ARF, 60ins 16, was restricted to the cytoplasm, did not stabilize p53 and was unable t o arrest the growth of a p53 expressing melanoma cell line. This is the fir st example of an exon 1 beta mutation that inactivates p14ARF, and thus imp licates a role for this tumour suppressor in melanoma predisposition.