title: Increased Stability of Nucleolar PinX1 in the Presence of TERT.
abstract: PinX1, a nucleolar protein of 328 amino acids, inhibits telomerase activity, which leads to the shortening of telomeres. The C-terminal region of PinX1 is responsible for its nucleolar localization and binding with TERT, a catalytic component of telomerase. A fraction of TERT localizes to the nucleolus, but the role of TERT in the nucleolus is largely unknown. Here, we report a functional connection between PinX1 and TERT regarding PinX1 stability. The C-terminal of PinX1(205-328), a nucleolar fragment, was much more stable than the N-terminal of PinX1(1-204), a nuclear fragment. Interestingly, PinX1 was less stable in TERT-depleted cells and more stable in TERT-myc expressing cells. Stability assays for PinX1 truncation forms showed that both PinX1(1-328) and PinX1(205-328), nucleolar forms, were more rapidly degraded in TERT-depleted cells, while they were more stably maintained in TERT-overexpressing cells, compared to each of the controls. However, PinX1(1-204) was degraded regardless of the TERT status. These results reveal that the stability of PinX1 is maintained in nucleolus in the presence of TERT and suggest a role of TERT in the regulation of PinX1 steady-state levels.
authors.affiliation: Department of Bioscience and Biotechnology, Konkuk University, Seoul 143-701, Korea.
authors.forename: Ponnarath
authors.initials: P
authors.lastname: Keo
authors.affiliation: Department of Obstetrics and Gynecology, Hanyang University College of Medicine, Seoul 133-791, Korea.|Institute of Medical Science, Hanyang University College of Medicine, Seoul 133-791, Korea.
authors.forename: Joong Sub
authors.initials: JS
authors.lastname: Choi
authors.affiliation: Department of Obstetrics and Gynecology, Hanyang University College of Medicine, Seoul 133-791, Korea.|Institute of Medical Science, Hanyang University College of Medicine, Seoul 133-791, Korea.
authors.forename: Jaeman
authors.initials: J
authors.lastname: Bae
authors.affiliation: Department of Bioscience and Biotechnology, Konkuk University, Seoul 143-701, Korea.
authors.forename: Yhong-Hee
authors.initials: YH
authors.lastname: Shim
authors.affiliation: Institute of Medical Science, Hanyang University College of Medicine, Seoul 133-791, Korea.
authors.forename: Bong-Kyeong
authors.initials: BK
authors.lastname: Oh
mesh_terms: D018797:Cell Cycle Proteins; D002466:Cell Nucleolus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D019098:Telomerase / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; C440808:PINX1 protein, human; D025521:Tumor Suppressor Proteins; C509186:TERT protein, human; D019098:Telomerase
keywords: PinX1; TERT; nucleolus; protein stability