Maternal embryonic leucine zipper kinase is stabilized in mitosis by phosphorylation and is partially degraded upon mitotic exit.
MELK (maternal embryonic leucine zipper kinase) is a cell cycle dependent protein kinase involved in diverse cell processes including cell proliferation, apoptosis, cell cycle and mRNA processing. Noticeably, MELK expression is increased in cancerous tissues, upon cell transformation and in mitotically-blocked cells. The question of how MELK protein level is controlled is therefore important. Here, we show that MELK protein is restricted to proliferating cells derived from either cancer or normal tissues and that MELK protein level is severely decreased concomitantly with other cell cycle proteins in cells which exit the cell cycle. Moreover, we demonstrate in human HeLa cells and Xenopus embryos that approximately half of MELK protein is degraded upon mitotic exit whereas another half remains stable during interphase. We show that the stability of MELK protein in M-phase is dependent on its phosphorylation state.
Badouel
Caroline
C
CNRS UMR 6061 Génétique et Développement, Université de Rennes 1, IFR140 GFAS, Faculté de médecine, 2 avenue du Professeur Léon Bernard, CS 34317, 35043 Rennes Cedex, France.
Chartrain
Isabelle
I
Blot
Joëlle
J
Tassan
Jean-Pierre
JP
D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000201:enzymology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000201:enzymology*; D005306:Fertilization; D006367:HeLa Cells; D006801:Humans; D008297:Male; D008938:Mitosis / Q000502:physiology*; D010766:Phosphorylation; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014471:Umbilical Veins / Q000166:cytology / Q000201:enzymology; D014982:Xenopus laevis / Q000254:growth & development / Q000378:metabolism
C484610:MELK protein, human; D017346:Protein Serine-Threonine Kinases