Nuclear import of htert requires a bipartite nuclear localization signal and Akt-mediated phosphorylation

Jeeyun Chung, Prabhat Khadka, In Kwon Chung

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

Sustained cell proliferation requires telomerase to maintain functional telomeres that are essential for chromosome integrity and protection. Although nuclear import of telomerase transcriptase (hTERT) is required for telomerase activity to elongate telomeres in vivo, the molecular mechanism regulating nuclear localization of hTERT is unclear. We have identified a bipartite nuclear localization signal (NLS; amino acid residues 222-240) that is responsible for nuclear import of hTERT. Immunofluorescence imaging of hTERT revealed that mutations in any of the bipartite NLS sequences result in decreased nuclear fluorescence intensity compared with wild-type hTERT. We also show that Akt-mediated phosphorylation at serine 227 is necessary for directing nuclear translocation of hTERT. Interestingly, serine 227 is located between two clusters of basic amino acids in the bipartite NLS. Inactivation of Akt activity by a dominant-negative mutant or wortmannin treatment attenuated nuclear localization of hTERT. We further show that both bipartite NLS and serine 227 in hTERT are required for cell immortalization of normal human foreskin fibroblast cells. Taken together, our findings reveal a previously unknown regulatory mechanism for nuclear import of hTERT through a bipartite NLS mediated by Akt phosphorylation, which represents an alternative pathway for modulating telomerase activity in cancer.

Original languageEnglish
Pages (from-to)2684-2697
Number of pages14
JournalJournal of Cell Science
Volume125
Issue number11
DOIs
Publication statusPublished - 2012 Jun 1

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Nuclear Localization Signals
Cell Nucleus Active Transport
Telomerase
Phosphorylation
Serine
Telomere
Foreskin
Basic Amino Acids
DNA-Directed RNA Polymerases
Fluorescent Antibody Technique
Fibroblasts
Chromosomes
Fluorescence
Cell Proliferation
Amino Acids
Mutation
Neoplasms
Therapeutics

All Science Journal Classification (ASJC) codes

  • Cell Biology

Cite this

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abstract = "Sustained cell proliferation requires telomerase to maintain functional telomeres that are essential for chromosome integrity and protection. Although nuclear import of telomerase transcriptase (hTERT) is required for telomerase activity to elongate telomeres in vivo, the molecular mechanism regulating nuclear localization of hTERT is unclear. We have identified a bipartite nuclear localization signal (NLS; amino acid residues 222-240) that is responsible for nuclear import of hTERT. Immunofluorescence imaging of hTERT revealed that mutations in any of the bipartite NLS sequences result in decreased nuclear fluorescence intensity compared with wild-type hTERT. We also show that Akt-mediated phosphorylation at serine 227 is necessary for directing nuclear translocation of hTERT. Interestingly, serine 227 is located between two clusters of basic amino acids in the bipartite NLS. Inactivation of Akt activity by a dominant-negative mutant or wortmannin treatment attenuated nuclear localization of hTERT. We further show that both bipartite NLS and serine 227 in hTERT are required for cell immortalization of normal human foreskin fibroblast cells. Taken together, our findings reveal a previously unknown regulatory mechanism for nuclear import of hTERT through a bipartite NLS mediated by Akt phosphorylation, which represents an alternative pathway for modulating telomerase activity in cancer.",
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Nuclear import of htert requires a bipartite nuclear localization signal and Akt-mediated phosphorylation. / Chung, Jeeyun; Khadka, Prabhat; Chung, In Kwon.

In: Journal of Cell Science, Vol. 125, No. 11, 01.06.2012, p. 2684-2697.

Research output: Contribution to journalArticle

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