| Modification Notes |
The Plk (polo-like kinase) family consists of serine/threonine kinases that are closely related to polo and CDC5 proteins, which are required for passage through mitosis in Drosophila and Saccharomyces, respectively. Polo-like kinases, which include Plk, Snk (serum-inducible kinase, also designated Plk2), Fnk (FGF-inducible kinase, also designated Plk3 or PRK) and Sak (also designated Plk4), all play a role in cell proliferation. Sak differs from other polo-like kinases because it has only a single polo box, which forms a dimer fold that resides in the nucleolus, centrosomes, and the cleavage furrow. Sak expression slowly increases during S through M phase, and Sak mediates late mitotic progression, cell survival, and postgastrulation embryonic development. APC/C destroys Sak by proteolysis. Reduced Sak expression causes increased incidence of apoptosis and anaphase arrest, while haploinsufficiency of the Sak gene causes spontaneous tumors to develop, primarily in the liver. |