Overexpression of the human MNB/DYRK1A gene induces formation of multinucleate cells through overduplication of the centrosome.
BACKGROUND
Previously we cloned the human MNB/DYRK1A gene from the "Down syndrome critical region" on chromosome 21. This gene encodes a dual specificity protein kinase that catalyzes its autophosphorylation on serine/threonine and tyrosine residues. But, the functions of the MNB/DYRK1A gene in cellular processes are unknown.


RESULTS
In this study, we examined HeLa cells transfected with cDNA encoding a green fluorescent protein (GFP)-MNB/DYRK1A fusion protein and found 2 patterns of expression: In one group of transfected cells, GFP-MNB/DYRK1A was localized as dots within the nucleus; and in the other group, it was overexpressed and had accumulated all over the nucleus. In the cells overexpressing GFP-MNB/DYRK1A, multinucleation was clearly observed; whereas in those with the nuclear dots, such aberrant nuclei were not found. Furthermore, in the latter cells, essential processes such as mitosis and cytokinesis occurred normally. Multinucleation was dependent on the kinase activity of MNB/DYRK1A, because it was not observed in cells overexpressing kinase activity-negative mutants, GFP-MNB/DYRK1A (K179R) and GFP-MNB/DYRK1A (Y310F/Y312F). Immunostaining of GFP-MNB/DYRK1A-overexpressing cells with specific antibodies against alpha- and gamma-tubulin revealed that multiple copies of centrosomes and aberrant multipolar spindles were generated in these cells.


CONCLUSIONS
These results indicate that overexpression of MNB/DYRK1A induces multinucleation in HeLa cells through overduplication of the centrosome during interphase and production of aberrant spindles and missegregation of chromosomes during mitosis.
Funakoshi
Eishi
E
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Setsunan University, Osaka 573-0101, Japan. funakos@pharm.setsunan.ac.jp
Hori
Takamitsu
T
Haraguchi
Tokuko
T
Hiraoka
Yasushi
Y
Kudoh
Jun
J
Shimizu
Nobuyoshi
N
Ito
Fumiaki
F
D002453:Cell Cycle; D002467:Cell Nucleus / Q000201:enzymology / Q000648:ultrastructure*; D018385:Centrosome / Q000648:ultrastructure*; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D008870:Microtubules / Q000648:ultrastructure; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D000097603:Dyrk Kinases
D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D000097603:Dyrk Kinases