title: Identification of PITX1 as a TERT suppressor gene located on human chromosome 5.
abstract: Telomerase, a ribonucleoprotein enzyme that maintains telomere length, is crucial for cellular immortalization and cancer progression. Telomerase activity is attributed primarily to the expression of telomerase reverse transcriptase (TERT). Using microcell-mediated chromosome transfer (MMCT) into the mouse melanoma cell line B16F10, we previously found that human chromosome 5 carries a gene, or genes, that can negatively regulate TERT expression (H. Kugoh, K. Shigenami, K. Funaki, J. Barrett, and M. Oshimura, Genes Chromosome Cancer 36:37-47, 2003). To identify the gene responsible for the regulation of TERT transcription, we performed cDNA microarray analysis using parental B16F10 cells, telomerase-negative B16F10 microcell hybrids with a human chromosome 5 (B16F10MH5), and its revertant clones (MH5R) with reactivated telomerase. Here, we report the identification of PITX1, whose expression leads to the downregulation of mouse tert (mtert) transcription, as a TERT suppressor gene. Additionally, both human TERT (hTERT) and mouse TERT (mtert) promoter activity can be suppressed by PITX1. We show that three and one binding site within the hTERT and mtert promoters, respectively, that express a unique conserved region are responsible for the transcriptional activation of TERT. Furthermore, we showed that PITX1 binds to the TERT promoter both in vitro and in vivo. Thus, PITX1 suppresses TERT transcription through direct binding to the TERT promoter, which ultimately regulates telomerase activity.
authors.affiliation: Department of Biomedical Science, Graduate School of Medical Science, Tottori University, 86 Nishicho, Yonago 683-8503, Japan.
authors.forename: Dong-Lai
authors.initials: DL
authors.lastname: Qi
authors.forename: Takahito
authors.initials: T
authors.lastname: Ohhira
authors.forename: Chikako
authors.initials: C
authors.lastname: Fujisaki
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Inoue
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Ohta
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Osaki
authors.forename: Eriko
authors.initials: E
authors.lastname: Ohshiro
authors.forename: Tomomi
authors.initials: T
authors.lastname: Seko
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Aoki
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Oshimura
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kugoh
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002895:Chromosomes, Human, Pair 5; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D051761:Paired Box Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D051761:Paired Box Transcription Factors; D012333:RNA, Messenger; C101485:homeobox protein PITX1; C509186:TERT protein, human; D019098:Telomerase; C509187:Tert protein, mouse