EXPRESSION PROFILE OF THE PUTATIVE CATALYTIC SUBUNIT OF THE TELOMERASE GENE

Telomerase, a ribonucleoprotein complex, adds hexameric repeats called telomeres to the growing ends of chromosomal DNA, The enzyme telomera se activity Is present in a vast majority of tumors but is repressed i n most normal tissues, Recently, two groups have reported the molecula r cloning of the putative catalytic subunit (hEST2/hTRT) of the telome rase gene, We investigated the expression of this gene in diverse tumo r-derived cell lines and tumors as well as in various normal tissues, The expression of hEST2/hTRT was detectable in tumor-derived cell line s, primary breast tumors, pancreatic tumors, and kidney tumors, Furthe rmore, the expression of hEST2/hTRT was down-regulated in response to a differentiation inducer, However, several normal tissues also expres sed varying levels of hEST2/hTRT, Early passage cultures of endothelia l fibroblasts and some epithelial cells also expressed the telomerase gene, albeit at low levels, In contrast, the expression of TLP1/TP1, t he human homologue of Tetrahymena p80 telomerase subunit, was similar in all of these samples, Our results indicate that the differences in expression of hEST2/hTRT in tumor versus normal cells are relative and are not absolute.