Phosphorylation of myosin-II regulatory light chain by cyclin-p34cdc2: a mechanism for the timing of cytokinesis.
To understand how cytokinesis is regulated during mitosis, we tested cyclin-p34cdc2 for myosin-II kinase activity, and investigated the mitotic-specific phosphorylation of myosin-II in lysates of Xenopus eggs. Purified cyclin-p34cdc2 phosphorylated the regulatory light chain of cytoplasmic and smooth muscle myosin-II in vitro on serine-1 or serine-2 and threonine-9, sites known to inhibit the actin-activated myosin ATPase activity of smooth muscle and nonmuscle myosin (Nishikawa, M., J. R. Sellers, R. S. Adelstein, and H. Hidaka. 1984. J. Biol. Chem. 259:8808-8814; Bengur, A. R., A. E. Robinson, E. Appella, and J. R. Sellers. 1987. J. Biol. Chem. 262:7613-7617; Ikebe, M., and S. Reardon. 1990. Biochemistry. 29:2713-2720). Serine-1 or -2 of the regulatory light chain of Xenopus cytoplasmic myosin-II was also phosphorylated in Xenopus egg lysates stabilized in metaphase, but not in interphase. Inhibition of myosin-II by cyclin-p34cdc2 during prophase and metaphase could delay cytokinesis until chromosome segregation is initiated and thus determine the timing of cytokinesis relative to earlier events in mitosis.
Satterwhite
L L
LL
Department of Cell Biology and Anatomy, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Lohka
M J
MJ
Wilson
K L
KL
Scherson
T Y
TY
Cisek
L J
LJ
Corden
J L
JL
Pollard
T D
TD
D000595:Amino Acid Sequence; D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002453:Cell Cycle; D002455:Cell Division; D016213:Cyclins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D016200:Maturation-Promoting Factor / Q000378:metabolism; D008969:Molecular Sequence Data; D009218:Myosins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D013379:Substrate Specificity; D013997:Time Factors; D014981:Xenopus
D016213:Cyclins; D016203:CDC2 Protein Kinase; D016200:Maturation-Promoting Factor; D009218:Myosins