title: Control mechanisms in the regulation of telomerase reverse transcriptase expression in differentiating human teratocarcinoma cells.
abstract: Telomerase is active in about 90% of cancers and contributes to the immortality of cancer cells by maintaining the lengths of the ends of chromosomes. Undifferentiated embryonic human teratocarcinoma (HT) cells were found to express high levels of hTERT, the catalytic subunit of telomerase, and the hTERT promoter was unmethylated in these cells. Retinoic acid (RA)-induced differentiation led to hTERT gene silencing and increased methylation of the hTERT promoter. Treatment with trichostatin A, a histone deacetylase inhibitor, resulted in hTERT reactivation only in very early differentiating HT cells. After methylation patterns had been established within the hTERT promoter region in late differentiating cells, 5-azacytidine, a common demethylating agent, activated the hTERT gene but trichostatin A had no effect on hTERT transcription. These studies suggest that histone deacetylation is involved in early hTERT gene down-regulation and that DNA methylation may maintain silencing of the hTERT gene in these cells.
authors.affiliation: Department of Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Nadejda G
authors.initials: NG
authors.lastname: Lopatina
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Poole
authors.forename: Sabita N
authors.initials: SN
authors.lastname: Saldanha
authors.forename: Nathaniel J
authors.initials: NJ
authors.lastname: Hansen
authors.forename: Jason S
authors.initials: JS
authors.lastname: Key
authors.forename: Mark A
authors.initials: MA
authors.lastname: Pita
authors.forename: Lucy G
authors.initials: LG
authors.lastname: Andrews
authors.forename: Trygve O
authors.initials: TO
authors.lastname: Tollefsbol
mesh_terms: D000970:Antineoplastic Agents / Q000378:metabolism; D001374:Azacitidine / Q000378:metabolism; D020134:Catalytic Domain; D002454:Cell Differentiation; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D006877:Hydroxamic Acids / Q000378:metabolism; D008745:Methylation; D011401:Promoter Regions, Genetic; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D018243:Teratocarcinoma / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D014212:Tretinoin / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D006877:Hydroxamic Acids; C012589:trichostatin A; D014212:Tretinoin; D004248:DNA (Cytosine-5-)-Methyltransferases; D019098:Telomerase; D001374:Azacitidine