The Aspergillus nidulans protein-serine/threonine kinase nimA (never in mitosis A) is required for entry into mitosis.
Cells with a nimA mutation arrest in G2, while overexpression of nimA induces mitosis.Like nimA and Nek1, NEK2 has an N-terminal catalytic domain and a very basic C-terminal region. Overall, NEK2
shares 36 to 38% sequence identity with nimA, Nek1, and human NEK3. Regulated by Hippo genes.
NCBI Summary:
This gene encodes a serine/threonine-protein kinase that is involved in mitotic regulation. This protein is localized to the centrosome, and undetectable during G1 phase, but accumulates progressively throughout the S phase, reaching maximal levels in late G2 phase. Alternatively spliced transcript variants encoding different isoforms with distinct C-termini have been noted for this gene. [provided by RefSeq, Feb 2011]
General function
Comment
Cellular localization
Cytoplasmic, Nuclear
Comment
Ovarian function
Oogenesis, Oocyte maturation
Comment
Nek2 and its substrate, centrobin/Nip2, are required for proper meiotic spindle formation of the mouse oocytes. Sonn S et al. SummaryA typical centrosome consists of a pair of centrioles embedded in a proteinous matrix called pericentriolar material. However, the centrosomes in the mouse oocytes and early embryos lack centrioles, but consist of the gamma-tubulin-enriched vesicle aggregates. We previously revealed that Nek2 and centrobin/Nip2, a centrosomal substrate of Nek2, is critical for the mouse early embryogenesis, especially at the step of spindle assembly during mitosis. In order to expand our understanding of the biological functions of Nek2, we examined expression and knockdown phenotypes of Nek2 and its substrates, centrobin and C-Nap1, in the mouse oocyte. Nek2, centrobin and C-Nap1 in the mouse oocytes were also centrosomal. Suppression of Nek2 and its substrates did not affect meiotic resumption of the oocytes. However, meiosis of the Nek2- and centrobin-suppressed oocytes was not completed, but arrested with defects in spindle assembly. No visible phenotype was observed in the C-Nap1-suppressed oocytes. These results indicate that Nek2 is critical for proper assembly of the meiotic spindles. Centrobin may be a possible substrate of Nek2 responsible for the meiotic spindle assembly in the mouse oocytes.
Fujioka T, et al 2000 reported the Nek2 expression and localization in porcine oocyte during
maturation.
The authors studied the role of the Ser/Thr protein kinase Nek2 on meiosis progression
by using in vitro porcine oocyte maturation system. Nek2 is a candidate of a
mammalian homologue of NIMA, which was found in Aspergillus nidulans as an
essential molecule for mitosis progression.
The Nek2 expression levels did not change through the oocyte maturation, but
fluorescence microscopy observation of Nek2 in the oocytes at various
maturation steps showed that Nek2 was detected only at metaphase II, but not
before metaphase II, At metaphase II, Nek2 was found exclusively on the
chromosomes. These results suggest that Nek2 changes the cellular localization
during maturation and accumulates on the chromosomes to play a role on the
entry and progression of metaphase II.