STRUCTURE AND METHYLATION-ASSOCIATED SILENCING OF A GENE WITHIN A HOMOZYGOUSLY DELETED REGION OF HUMAN-CHROMOSOME BAND 8P22

The structure and expression pattern of a human gene located within a homozygously deleted region of a metastatic prostate cancer have been characterized. Multiple cDNA fragments of this gene were isolated by h ybrid capture with yeast artificial chromosome clones covering the del etion region. Eleven coding exons spanned 205-220 kb of the 730- to 97 0-kb deletion. The predicted amino acid sequence was 43% identical to that of an anonymous Caenorhabditis elegans gene and 20% identical to an accessory or regulatory subunit of the oligosaccharyltransferase en zyme complex in Saccharomyces cerevisiae. Hydrophobicity profiles of a ll three gene products were similar and showed four putative membrane- spanning domains in the molecules' C-terminal halves, suggesting a gen eral conservation of function. The gene was expressed as an similar to 1.5kb mRNA in most nonlymphoid human cells/tissues including prostate , lung, liver, and colon. Expression was detected in many epithelial t umor cell lines, but was undetectable by Northern blot or RT-PCR in 14 of 15 colorectal, 1 of 8 lung, and 1 of 4 liver cancer cell lines. La ck of expression in tumor cell lines was highly correlated with hyperm ethylation of a CpG island located at the gene's 5' end. These finding s form a basis for further work on this candidate tumor suppressor gen e. (C) 1996 Academic Press, Inc.