A new β2 microglobulin mutation found in a melanoma tumor cell line

beta(2) microglobulin mutations are an important mechanism for HLA class I total loss, (phenotype No. I) and have been described in colon carcinomas, melanomas and lymphomas. We describe a new beta(2) microglobulin mutation detected in the melanoma cell line GR-34. The new mutation reported here was identified as a deletion of 4 bases (TTCT) in the highly repetitive sequence CTCTCTCTTTCT located in the leader sequence of the PZ microglobulin gene at codon 15-16 of exon 1, The mutation produces a frameshift in the open reading frame sequence with the appearance of a stop codon at position 42. We also demonstrate that the second beta(2) microglobulin gene is deleted, Comparisons with beta(2) microglobulin mutations in other tumor cell lines suggest a mutation hot spot in exon 1.