Caffeine overrides the S-phase cell cycle block in sea urchin embryos

Zygote ◽  
1997 ◽  
Vol 5 (2) ◽  
pp. 127-138 ◽  
Author(s):  
Rajnikant Patel ◽  
Elizabeth M. Wright ◽  
Michael Whitaker
Keyword(s):  
Protein Kinase ◽  
Sea Urchin ◽  
S Phase ◽  
Phase Cell ◽  
Protein Kinase Activity ◽  
Checkpoint Control ◽  
Cell Cycles ◽  
Sea Urchin Embryos ◽  
Sea Urchin Embryo ◽  
M Phase

SummaryDuring the early mitotic cell cycles of the sea urchin embryo, the cell oscillates between S-phase and M-phase. In the presence of aphidicolin, a DNA synthesis inhibitor, a checkpoint control blocks the activation of the p34cdc2 protein kinase, by keeping it in the inactive, tyrosine phosphorylated form, and the embryos do not enter mitosis. Caffeine has been shown to bypass the G2/M-phase checkpoint in mammalian cells and in cycling Xenopus extracts and to induce mitosis despite the presence of damaged or unreplicated DNA. In this study we show that caffeine also induces mitosis and cell division in sea urchin embryos, in the presence of unreplicated DNA, by stimulating the tyrosine dephosphorylation of p34cdc2 and switching on its protein kinase activity. We also show that the caffeine-induced activation of the p34cdc2 protein kinase is not mediated by either of the two second messengers, calcium and cAMP, or by inhibition of the p34cdc2 tyrosine kinase. Thus, none of the mechanisms proposed for caffeine's action can explain how it overrides the S-phase checkpoint in the early cell cycles of the sea urchin embryo.

Comparative studies of rat liver and sea urchin embryo nuclear matrices: partial fractionation and protein kinase activity distribution

1982 ◽  
Vol 55 (1) ◽  
pp. 189-198
Author(s):  
L. Sevaljevic ◽  
M. Petrovic ◽  
M. Konstantinovic ◽  
K. Krtolica
Keyword(s):  
Protein Kinase ◽  
Sea Urchin ◽  
Rat Liver ◽  
Kinase Activity ◽  
Matrix Proteins ◽  
Protein Kinase Activity ◽  
Structural Elements ◽  
Activity Distribution ◽  
Sea Urchin Embryo ◽  
The Matrix

Rat liver and sea urchin embryo nuclear matrices were found to differ in composition and in the strength of the association of their structural elements. Apart from the qualitative differences in composition, the embryonic matrices retained greater amounts of nuclear proteins and DNA, and were less susceptible to ultrasonic treatment than those of rat liver. They were essentially resistant to mild sonication, by which the rat liver matrix structure was resolved into two distinct fractions, referred to by Berezney (1980) as matricin and ribonucleoprotein (RNP). Both sub-fractions exhibited a protein kinase activity; the phosphorylating capacity of the RNP-associated protein kinases was found to be higher than that of the matricin-bound enzyme. The preferred substrate was among the secondary matrix proteins. In sea urchin embryos, sonication introduced no change in the type and lesion of the matrix proteins phosphorylated by the associated enzyme.

From Cdc2 to Cdk1: when did the cell cycle kinase join its cyclin partner?

2002 ◽  
Vol 115 (12) ◽  
pp. 2461-2464 ◽  
Author(s):  
Marcel Dorée ◽  
Tim Hunt
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Marine Invertebrate ◽  
Direct Proof ◽  
Protein Kinase Activity ◽  
Cell Cycles ◽  
M Phase ◽  
Long Time ◽  
Dependent Protein ◽  
Cyclin Partner

The idea that Cdc2 and cyclins play a key role in the control of the G2/M transition of the cell cycle came largely from genetic analysis of fission yeast and physiological studies of clam, frog, sea urchin and starfish eggs and oocytes. However, it took a long time to realise that Cdc2 and cyclins form a stoichiometric complex and that a cyclin subunit is necessary for the Cdc2 subunit to gain its protein kinase activity. Cyclins were first recognized as proteins whose abundance oscillates during the early cell cycles of marine invertebrate eggs and their connection with MPF (maturation-promoting factor), the entity defined in frog and starfish oocytes whose activity controls entry into M phase, was far from clear at first. Indeed, it was a long time before MPF was shown to be a protein kinase,and direct proof that MPF is a heterodimer comprising one molecule of cyclin and one molecule of Cdc2 was finally obtained only when the Cdc2-associated component of purified starfish MPF was sequenced and found to be cyclin B. When this fundamental discovery was confirmed in vertebrates and mammalian members of the Cdc2 family were also shown to bind cyclins, Cdc2 became Cdk1,the first cyclin-dependent protein kinase.

Cell cycle-specific induction of an 89 kDa serine/threonine protein kinase activity in Trypanosoma brucei

1994 ◽  
Vol 107 (7) ◽  
pp. 1825-1832
Author(s):  
M. Gale ◽  
V. Carter ◽  
M. Parsons
Keyword(s):  
Cell Cycle ◽  
Protein Synthesis ◽  
Protein Kinase ◽  
Protein Phosphorylation ◽  
Trypanosoma Brucei ◽  
S Phase ◽  
Protein Kinase Inhibitors ◽  
Phase Cell ◽  
Protein Kinase Activity ◽  
Serum Factors

The cell cycle compartmentalization of specific activities of the protozoan parasite Trypanosoma brucei has remained unexplored due to the lack of a cell synchronization protocol. We report here that stationary phase cells stimulated to enter the cell cycle showed significant synchrony through the first cycle. The pattern of tyrosine phosphorylated proteins, known to undergo alterations during trypanosome development, showed only moderate changes as quiescent cells entered the cycle, particularly an increase in a 77 kDa species. However, the activity of an 89 kDa protein kinase (SPK89), previously demonstrated to be restricted to the proliferative stages of the parasite's life cycle, markedly increased as the population entered S phase. Cell sorting experiments demonstrated that SPK89 activity was highest in S phase cells and moderate in G2/M cells. The entry into S phase and increased SPK89 activity did not depend on serum factors but required protein synthesis for a discrete period after stimulation. Various modulators of protein phosphorylation were tested to determine their effects on progression to S and SPK89 activity. Only staurosporine and genistein were effective. However, both of these compounds inhibited virtually all protein phosphorylation and protein synthesis in the parasites. Thus these drugs cannot be used as specific protein kinase inhibitors in trypanosomes.

scholarly journals Cell cycle tyrosine phosphorylation of p34cdc2 and a microtubule-associated protein kinase homolog in Xenopus oocytes and eggs.

1991 ◽  
Vol 11 (4) ◽  
pp. 1965-1971 ◽  
Author(s):  
J E Ferrell ◽  
M Wu ◽  
J C Gerhart ◽  
G S Martin
Keyword(s):  
Molecular Weight ◽  
Protein Kinase ◽  
Map Kinase ◽  
Tyrosine Phosphorylation ◽  
Time Course ◽  
Mitotic Cell ◽  
Mitogen Activated Protein Kinase ◽  
Xenopus Laevis Oocytes ◽  
Cell Cycles ◽  
M Phase

We have examined the time course of protein tyrosine phosphorylation in the meiotic cell cycles of Xenopus laevis oocytes and the mitotic cell cycles of Xenopus eggs. We have identified two proteins that undergo marked changes in tyrosine phosphorylation during these processes: a 42-kDa protein related to mitogen-activated protein kinase or microtubule-associated protein-2 kinase (MAP kinase) and a 34-kDa protein identical or related to p34cdc2. p42 undergoes an abrupt increase in its tyrosine phosphorylation at the onset of meiosis 1 and remains tyrosine phosphorylated until 30 min after fertilization, at which point it is dephosphorylated. p42 also becomes tyrosine phosphorylated after microinjection of oocytes with partially purified M-phase-promoting factor, even in the presence of cycloheximide. These findings suggest that MAP kinase, previously implicated in the early responses of somatic cells to mitogens, is also activated at the onset of meiotic M phase and that MAP kinase can become tyrosine phosphorylated downstream from M-phase-promoting factor activation. We have also found that p34 goes through a cycle of tyrosine phosphorylation and dephosphorylation prior to meiosis 1 and mitosis 1 but is not detectable as a phosphotyrosyl protein during the 2nd through 12th mitotic cell cycles. It may be that the delay between assembly and activation of the cyclin-p34cdc2 complex that p34cdc2 tyrosine phosphorylation provides is not needed in cell cycles that lack G2 phases. Finally, an unidentified protein or group of proteins migrating at 100 to 116 kDa increase in tyrosine phosphorylation throughout maturation, are dephosphorylated or degraded within 10 min of fertilization, and appear to cycle between low-molecular-weight forms and high-molecular-weight forms during early embryogenesis.

scholarly journals The Saccharomyces cerevisiae YAK1 gene encodes a protein kinase that is induced by arrest early in the cell cycle.

1991 ◽  
Vol 11 (8) ◽  
pp. 4045-4052 ◽  
Author(s):  
S Garrett ◽  
M M Menold ◽  
J R Broach
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Kinase Activity ◽  
Specific Activity ◽  
S Phase ◽  
Protein Kinase Activity ◽  
Dependent Protein Kinase ◽  
Protein Levels ◽  
Cycle Arrest ◽  
Dependent Protein

Null mutations in the gene YAK1, which encodes a protein with sequence homology to known protein kinases, suppress the cell cycle arrest phenotype of mutants lacking the cyclic AMP-dependent protein kinase (A kinase). That is, loss of the YAK1 protein specifically compensates for loss of the A kinase. Here, we show that the protein encoded by YAK1 has protein kinase activity. Yak1 kinase activity is low during exponential growth but is induced at least 50-fold by arrest of cells prior to the completion of S phase. Induction is not observed by arrest at stages later in the cell cycle. Depending on the arrest regimen, induction can occur either by an increase in Yak1 protein levels or by an increase in Yak1 specific activity. Finally, an increase in Yak1 protein levels causes growth arrest of cells with attenuated A kinase activity. These results suggest that Yak1 acts in a pathway parallel to that of the A kinase to negatively regulate cell proliferation.

scholarly journals A complex containing p34cdc2 and cyclin B phosphorylates the nuclear lamin and disassembles nuclei of clam oocytes in vitro.

1991 ◽  
Vol 112 (4) ◽  
pp. 523-533 ◽  
Author(s):  
G Dessev ◽  
C Iovcheva-Dessev ◽  
J R Bischoff ◽  
D Beach ◽  
R Goldman
Keyword(s):  
Protein Kinase ◽  
Hela Cells ◽  
Kinase Activity ◽  
Nuclear Lamina ◽  
Cyclin B ◽  
Protein Kinase Activity ◽  
Nuclear Lamin ◽  
Single Protein ◽  
M Phase

Cell-free extracts prepared from activated clam oocytes contain factors which induce phosphorylation of the single 67-kD lamin (L67), disassemble clam oocyte nuclei, and cause chromosome condensation in vitro (Dessev, G., R. Palazzo, L. Rebhun, and R. Goldman. 1989. Dev. Biol. 131:469-504). To identify these factors, we have fractionated the oocyte extracts. The nuclear lamina disassembly (NLD) activity, together with a protein kinase activity specific for L67, appear as a single peak throughout a number of purification steps. This peak also contains p34cdc2, cyclin B, and histone H1-kinase activity, which are components of the M-phase promoting factor (MPF). The NLD/L67-kinase activity is depleted by exposure of this purified material to Sepharose conjugated to p13suc1, and is restored upon addition of a p34cdc2/p62 complex from HeLa cells. The latter complex phosphorylates L67 and induces NLD in the absence of other clam oocyte proteins. Our results suggest that a single protein kinase activity (p34cdc2-H1 kinase, identical with MPF) phosphorylates the lamin and is involved in the meiotic breakdown of the nuclear envelope in clam oocytes.

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