Importin 7 and Nup358 Promote Nuclear Import of the Protein Component of Human Telomerase

• Published in: PloS one Vol. 9; no. 2; p. e88887
• Main Authors: Frohnert, Cornelia, Hutten, Saskia, Wälde, Sarah, Nath, Annegret, Kehlenbach, Ralph H.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 20.02.2014; Public Library of Science (PLoS)
• Subjects: Active Transport, Cell Nucleus - physiology; Adapter proteins; Amino acids; Biology; Cancer; Cell cycle; Cells; Deoxyribonucleic acid; DNA; DNA binding proteins; DNA sequencing; Enzymes; Filaments; Fluorescent Antibody Technique; Function analysis; HeLa Cells; Humans; Immunoprecipitation; Imports; Karyopherins - metabolism; Localization; Medicine; Molecular biology; Molecular Chaperones - metabolism; Nuclear Localization Signals - genetics; Nuclear Pore Complex Proteins - metabolism; Nuclear transport; Nucleotide sequence; Nucleotide sequencing; Protein transport; Receptors; Receptors, Cytoplasmic and Nuclear - metabolism; Ribonucleic acid; RNA; RNA Interference; RNA, Small Interfering - genetics; siRNA; Structure-function relationships; Telomerase; Telomerase - metabolism; Telomerase reverse transcriptase; Telomeres; Transport; Zinc; Zinc finger proteins
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0088887

In actively dividing eukaryotic cells, chromosome ends (telomeres) are subject to progressive shortening, unless they are maintained by the action of telomerase, a dedicated enzyme that adds DNA sequence repeats to chromosomal 3'end. For its enzymatic function on telomeres, telomerase requires nuclear import of its protein component (hTERT in human cells) and assembly with the RNA component, TERC. We now confirm a major nuclear localization signal (NLS) in the N-terminal region of hTERT and describe a novel one in the C-terminal part. Using an siRNA approach to deplete several import receptors, we identify importin 7 as a soluble nuclear transport factor that is required for efficient import. At the level of the nuclear pore complex (NPC), Nup358, a nucleoporin that forms the cytoplasmic filaments of the NPC, plays an important role in nuclear import of hTERT. A structure-function analysis of Nup358 revealed that the zinc finger region of the nucleoporin is of particular importance for transport of hTERT. Together, our study sheds light on the nuclear import pathway of hTERT.