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Prointerleukin-16 contains a functional CcN motif that regulates nuclear localization
Kevin C Wilson1, William W Cruikshank, David M Center
1The Pulmonary Center, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA. KWilson@lung.bumc.bu.edu
Biochemistry
|November 27, 2002
Summary
Interleukin-16 (IL-16) precursor protein localization is regulated by a novel dual phosphorylation-dependent CcN motif. This motif controls nuclear entry and cell cycle arrest, offering new insights into cytokine precursor function.
Area of Science:
- Cell Biology
- Molecular Biology
- Immunology
Background:
- Interleukin-16 (IL-16) is an immunomodulatory cytokine derived from a precursor, pro-IL-16.
- The N-terminal domain of pro-IL-16 translocates to the nucleus after caspase 3 cleavage, inducing cell cycle arrest.
- A nuclear localization sequence (NLS) was previously identified in the N-terminal domain.
Purpose of the Study:
- To investigate the regulatory mechanisms of pro-IL-16 nuclear localization.
- To identify and characterize novel functional motifs within the pro-IL-16 N-terminal domain.
- To elucidate the role of phosphorylation in regulating pro-IL-16 function.
Main Methods:
- Site-directed mutagenesis to alter putative phosphorylation sites.
- Analysis of protein localization using cellular imaging techniques.
- Assessment of cell cycle progression and arrest.
Main Results:
- A dual phosphorylation-regulated CcN motif, comprising protein kinase CK2 and cdc2 kinase substrate sites alongside the NLS, was identified.
- This CcN motif regulates the nuclear localization of pro-IL-16.
- Mutation of either phosphorylation site impaired the N-terminal domain's ability to induce G(0)/G(1) cell cycle arrest.
Conclusions:
- This study describes the first functional CcN motif identified in a cytokine precursor.
- The CcN motif plays a critical role in regulating pro-IL-16 nuclear import and subsequent cell cycle arrest.
- Phosphorylation of the CcN motif is essential for the biological activity of the pro-IL-16 N-terminal domain.