Late mitotic failure in mice lacking Sak, a polo-like kinase.
Polo-like kinases in yeast, flies, and mammals regulate key events in mitosis. Such events include spindle formation at G2/M, the anaphase-promoting complex (APC) at the exit from mitosis, the cleavage structure at cytokinesis, and DNA damage checkpoints in G2/M. Polo-like kinases are distinguished by two C-terminal polo box (pb) motifs, which localize the enzymes to mitotic structures. We previously identified Sak, a novel polo-like kinase found in Drosophila and mammals. Here, we demonstrate that the Sak kinase has a functional pb domain that localizes the enzyme to the nucleolus during G2, to the centrosomes in G2/M, and to the cleavage furrow during cytokinesis. To study the role of Sak in embryo development, we generated a Sak null allele, the first polo-like kinase to be mutated in mice. Sak(-/-) embryos arrested after gastrulation at E7.5, with a marked increase in mitotic and apoptotic cells. Sak(-/-) embryos displayed cells in late anaphase or telophase that continued to express cyclin B1 and phosphorylated histone H3. Our results suggest that Sak is required for the APC-dependent destruction of cyclin B1 and for exit from mitosis in the postgastrulation embryo.
Hudson
J W
JW
Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, M5G 1X5, Ontario, Canada.
Kozarova
A
A
Cheung
P
P
Macmillan
J C
JC
Swallow
C J
CJ
Cross
J C
JC
Dennis
J W
JW
D016475:3T3 Cells; D000595:Amino Acid Sequence; D064173:Anaphase-Promoting Complex-Cyclosome; D000818:Animals; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D029721:Drosophila Proteins; D006657:Histones / Q000378:metabolism; D006801:Humans; D008025:Ligases; D051379:Mice; D018345:Mice, Knockout; D008938:Mitosis / Q000502:physiology*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases
C534699:CCNB1 protein, human; C534700:Ccnb1 protein, mouse; C503698:CycB protein, Drosophila; D019926:Cyclin B; D056744:Cyclin B1; D029721:Drosophila Proteins; D006657:Histones; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases; C490219:PLK4 protein, human; C088051:Plk4 protein, mouse; D017346:Protein Serine-Threonine Kinases; D008025:Ligases