TRAFFICKING Spatiotemporal Dynamics of Casein Kinase 2

Protein casein kinase 2 (CK2), a multifunctional enzyme commonly considered a stable tetramer with two catalytic subunits and two regulatory ß subunits, has substrates in various cellular compartments. Filhol et al. used live-cell fluorescence imaging to track the subcellular localization of CK2 subunit mutants labeled with green fluorescent protein (GFP) or GFP derivatives. They found that nuclear import and export of CK2 and ß subunits were regulated independently. GFP-CK2 constructs transfected into NIH 3T3 cells were predominantly localized to the nucleus, a localization that depended in part on a functional nuclear localization signal in the CK2 NH₂-terminal region, and microinjected His₆-tagged GFP-CK2 rapidly translocated to the nucleus. CK2ß also accumulated in the nucleus; this depended on a zinc finger motif involved in CK2ß dimerization, but did not depend on CK2ß association with CK2. The authors fused stably transfected NIH 3T3 cells with untransfected HeLa cells to demonstrate shuttling of CK2, but not CK2ß, between the nucleus and the cytoplasm. Dual-color image analysis of differently labeled cotransfected and ß subunits, however, showed a predominantly cytoplasmic location for both subunits, and the microinjected holoenzyme, unlike the individual subunits, did not accumulate in the nucleus. Fibroblast growth factor 2, which binds to and activates the holoenzyme, triggered nuclear accumulation. Association of CK2ß with CK2, which is known to affect CK2 substrate specificity, may thus also regulate the subcellular distribution of CK2 and thereby its accessibility to various substrates.

O. Filhol, A. Nueda, V. Martel, D. Gerber-Scokaert, M. J. Benitez, C. Souchier, Y. Saoudi, C. Cochet, Live-cell fluorescence imaging reveals the dynamics of protein kinase CK2 individual subunits. Mol. Cell. Biol. 23, 975-987 (2003). [Abstract] [Full Text]

The editors suggest the following Related Resources on Science sites:

VIRTUAL JOURNAL
Live-Cell Fluorescence Imaging Reveals the Dynamics of Protein Kinase CK2 Individual Subunits

Odile Filhol, Arsenio Nueda, Véronique Martel, Delphine Gerber-Scokaert, Maria José Benitez, Catherine Souchier, Yasmina Saoudi, and Claude Cochet (1 February 2003)
Mol. Cell. Biol. 23 (3), 975. [DOI: 10.1128/MCB.23.3.975-987.2003]
 |  Abstract »  |  Full Text »  |  PDF »