title: Human chromosome 5 carries a putative telomerase repressor gene.
abstract: Telomerase, the ribonucleoprotein enzyme that maintains the telomere, is active in human germ and stem cells and in a majority of tumor tissues and immortalized cell lines. In contrast, telomerase activity is not detected in most somatic cells, suggesting that normal human cells contain a regulatory factor(s) to repress this activity. To identify which human chromosomes carry a gene or genes that function as telomerase repressors, we investigated telomerase activity in hybrids of the B16-F10 cell line, which contain individual human chromosomes transferred previously by microcell fusion and therefore represent a hybrid panel for the entire genome except for the Y chromosome. Microcell hybrids with an introduced normal human chromosome 5 showed inhibition of telomerase activity, but clones at a late passage exhibited reactivation of telomerase activity. Reactivation of telomerase activity was accompanied by deletion and/or rearrangement of the transferred human chromosome 5. The introduction of other human chromosomes did not significantly affect the telomerase activity of B16-F10 cells. The effect of suppression of telomerase activity in microcell hybrids containing chromosome 5 was accompanied by a reduction in the level of mTERT mRNA, which encodes a component of the telomerase complex. The putative telomerase repressor gene was mapped to human chromosome bands 5p11-p13 by a combination of functional analysis using transfer of subchromosomal transferable fragments of chromosome 5 into B16-F10 cells and deletion mapping of revertant clones with reactivated telomerase activity. Thus, these results suggest that loss of a gene(s) on this chromosome was responsible for telomerase reactivation, indicating that human chromosome 5 contains a gene or genes that can regulate the expression of mTERT in B16-F10 cells.
authors.affiliation: Department of Molecular and Cell Genetics, School of Life Sciences, Faculty of Medicine, Tottori University, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kugoh
authors.forename: Katsuyo
authors.initials: K
authors.lastname: Shigenami
authors.forename: Kenji
authors.initials: K
authors.lastname: Funaki
authors.forename: J Carl
authors.initials: JC
authors.lastname: Barrett
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Oshimura
mesh_terms: D000818:Animals; D020134:Catalytic Domain / Q000235:genetics; D002460:Cell Line; D002874:Chromosome Mapping / Q000379:methods; D002895:Chromosomes, Human, Pair 5 / Q000235:genetics*; D002999:Clone Cells; D004268:DNA-Binding Proteins; D004794:Enzyme Repression / Q000235:genetics; D020869:Gene Expression Profiling / Q000379:methods; D006801:Humans; D006822:Hybrid Cells; D008546:Melanoma, Experimental / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D051379:Mice; D012097:Repressor Proteins / Q000235:genetics* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D019098:Telomerase / Q000037:antagonists & inhibitors* / Q000096:biosynthesis* / Q000235:genetics; D014162:Transfection / Q000379:methods; D014407:Tumor Cells, Cultured
chemical_list: D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D019098:Telomerase