polo encodes a protein kinase homolog required for mitosis in Drosophila.

Abstract

We show that mutation in polo leads to a variety of abnormal mitoses in Drosophila larval neuroblasts. These include otherwise normal looking mitotic spindles upon which chromosomes appear overcondensed; normal bipolar spindles with polyploid complements of chromosomes; bipolar spindles in which one pole can be unusually broad; and monopolar spindles. We have cloned the polo gene from a mutant allele carrying a P-element transposon and sequenced cDNAs corresponding to transcripts of the wild-type locus. The sequence shows that polo encodes a 577-amino-acid protein with an amino-terminal domain homologous to a serine-threonine protein kinase, polo transcripts are abundant in tissues and developmental stages in which there is extensive mitotic activity. The transcripts show no obvious spatial pattern of distribution in relation to the mitotic domains of cellularized embryos but are specifically concentrated in dividing cells in larval discs and brains. In the cell cycles of both syncytial and cellularized embryos, the polo kinase undergoes cell cycle-dependent changes in its distribution: It is predominantly cytoplasmic during interphase; it becomes associated with condensed chromosomes toward the end of prophase; and it remains associated with chromosomes until telophase, whereupon it becomes cytoplasmic.

Protein kinases in control of the centrosome cycle

“…While polo mutations lead to a diverse array of mitotic spindle abnormalities in Drosophila embryos, the frequent appearance of monopolar spindles suggests that part of this defect emanates from the inability to separate centrosomes [18,19]. The same result is seen in ¢ssion yeast where loss of Plo1, the Schizosaccharomyces pombe Plk, also induces monopolar spindle formation with unseparated spindle poles [20].…”

Adhesion induced expression of the serine/threonine kinase Fnk in human macrophages

“…The Drosophila gene polo and the yeast cell cycle genes Cdc5 and plo1 encode related protein kinases which are required for progression through mitosis (Sunkel and Glover, 1988;Llamazares et al, 1991;Fenton and Glover, 1993;Kitada et al, 1993;Ohkura et al, 1995;Toczyski et al, 1997). In recent studies mammalian protein kinases have been identi®ed which are homologous to the Drosophila gene polo (Simmons et al, 1992;Clay et al, 1993;Lake and Jelinek, 1993;Golsteyn et al, 1994;Hamanaka et al, 1994;Holtrich et al, 1994).…”

The physical association and phosphorylation of Cdc25C protein phosphatase by Prk

“…In the past few years, an emerging family of protein kinases (the polo kinase family) has been described in yeast (Kitada et al, 1993), Drosophila (Llamazares et al, 1991), Xenopus (Kumagai and Dunphy, 1996), mouse (Simmons et al, 1992;Golsteyn et al, 1995;Donohue et al, 1995), and human (Hamanaka et al, 1994;Li et al, 1996; also see recent review Nigg, 1998). The Drosophila polo gene, homologous to the budding yeast Cdc5, encodes a serine/threonine (Ser/Thr) kinase and is required for mitosis in this species; mutations in this gene result in abnormal mitotic and meiotic division (Fenton and Glover, 1993).…”

“…The Drosophila polo gene, homologous to the budding yeast Cdc5, encodes a serine/threonine (Ser/Thr) kinase and is required for mitosis in this species; mutations in this gene result in abnormal mitotic and meiotic division (Fenton and Glover, 1993). The abnormalities of these mutants are manifested as over-condensed chromosomes, abnormal spindle formation, and polyploidy (Llamazares et al, 1991;Fenton and Glover, 1993). polo transcripts are abundantly expressed in tissues and developmental stages that display extensive mitotic activity.…”

“…polo transcripts are abundantly expressed in tissues and developmental stages that display extensive mitotic activity. The polo kinase activity peaks cyclically at anaphase/telophase (Llamazares et al, 1991;Fenton and Glover, 1993).…”