A mitotic cascade of NIMA family kinases. Nercc1/Nek9 activates the Nek6 and Nek7 kinases.
The Nek family of protein kinases in humans is composed of 11 members that share an amino-terminal catalytic domain related to NIMA, an Aspergillus kinase involved in the control of several aspects of mitosis, and divergent carboxyl-terminal tails of varying length. Nek6 (314AA) and Nek7 (303AA), 76% identical, have little noncatalytic sequence but bind to the carboxyl-terminal noncatalytic tail of Nercc1/Nek9, a NIMA family protein kinase that is activated in mitosis. Microinjection of anti-Nercc1 antibodies leads to spindle abnormalities and prometaphase arrest or chromosome missegregation. Herein we show that Nek6 is increased in abundance and activity during mitosis; activation requires the phosphorylation of Ser206 on the Nek6 activation loop. This phosphorylation and the activity of recombinant Nek6 is stimulated by coexpression with an activated mutant of Nercc1. Moreover, Nercc1 catalyzes the direct phosphorylation of prokaryotic recombinant Nek6 at Ser206 in vitro concomitant with 20-25-fold activation of Nek6 activity; Nercc1 activates Nek7 in vitro in a similar manner. Nercc1/Nek9 is likely to be responsible for the activation of Nek6 during mitosis and probably participates in the regulation of Nek7 as well. These findings support the conclusion that Nercc1/Nek9 and Nek6 represent a novel cascade of mitotic NIMA family protein kinases whose combined function is important for mitotic progression.
Belham
Christopher
C
Department of Molecular Biology and Medical Services, Massachusetts General Hospital, and Harvard Medical School, Boston, Massachusetts 02114, USA.
Roig
Joan
J
Caldwell
Jennifer A
JA
Aoyama
Yumi
Y
Kemp
Bruce E
BE
Comb
Michael
M
Avruch
Joseph
J
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018797:Cell Cycle Proteins; D002460:Cell Line; D017931:DNA Primers; D004789:Enzyme Activation; D006801:Humans; D007700:Kinetics; D051379:Mice; D008938:Mitosis; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D000072380:NIMA-Related Kinase 1; D000072379:NIMA-Related Kinases; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity
D018797:Cell Cycle Proteins; D017931:DNA Primers; D011994:Recombinant Proteins; C000606914:NEK1 protein, human; C512685:NEK7 protein, human; C462119:NEK9 protein, human; D000072380:NIMA-Related Kinase 1; D000072379:NIMA-Related Kinases; C442331:NIMA-related kinase 6; C000606920:Nek1 protein, mouse; C512686:Nek7 protein, mouse; D017346:Protein Serine-Threonine Kinases