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At least 271 records · Page 15Linked to original sources
PubMed1995

Chromosome condensation induced by fostriecin does not require p34cdc2 kinase activity and histone H1 hyperphosphorylation, but is associated with enhanced histone H2A and H3 phosphorylation.

Chromosome condensation at mitosis correlates with the activation of p34cdc2 kinase, the hyperphosphorylation of histone H1 and the phosphorylation of histone H3. Chromosome condensation can also be induced by treating interphase cells with the protein phosphatase 1 and 2A inhibitors okadaic acid and fostriecin. Mouse mammary tumour FT210 cells grow normally at 32 degrees C, but at 39 degrees C they lose p34cdc2 kinase activity and arrest in G2 because of a temperature-sensitive lesion in the cdc2 gene. The treatment of these G2-arrested FT210 cells with fostriecin or okadaic acid resulted in full chromosome condensation in the absence of p34cdc2 kinase activity or histone H1 hyperphosphorylation. However, phosphorylation of histones H2A and H3 was strongly stimulated, partly through inhibition of histone H2A and H3 phosphatases, and cyclins A and B were degraded. The cells were unable to complete mitosis and divide. In the presence of the protein kinase inhibitor starosporine, the addition of fostriecin did not induce histone phosphorylation and chromosome condensation. The results show that chromosome condensation can take place without either the histone H1 hyperphosphorylation or the p34cdc2 kinase activity normally associated with mitosis, although it requires a staurosporine-sensitive protein kinase activity. The results further suggest that protein phosphatases 1 and 2A may be important in regulating chromosome condensation by restricting the level of histone phosphorylation during interphase, thereby preventing premature chromosome condensation.

Alkaloids↗
PubMed1993

Cyclin A-mediated inhibition of intra-Golgi transport requires p34cdc2.

An in vitro assay was used to study the role of p34cdc2 in cyclin A-mediated vesicular transport inhibition. It was shown that the S-phase kinase p33cdk2 reduced the effect of cyclin A on transport assays performed with sHeLa cytosol, even though histone kinase was strongly activated. Also, transport with FT210 cytosol (which is temperature-sensitive for p34cdc2) was inhibited by cyclin A only at the permissive temperature. However, the phosphatase inhibitor microcystin inhibited transport without any requirement for p34cdc2 activity. These results show that transport is inhibited by cyclin A via p34cdc2, and also by another kinase, possibly downstream of p34cdc2.

Alkaloids↗
PubMed1988

Inhibitory effect of glycyrrhizin on polypeptide phosphorylation by polypeptide-dependent protein kinase (kinase P) in vitro.

The anti-viral mechanism of glycyrrhizin (GL) has been investigated by considering in vitro effects on polypeptide phosphorylation. It was found that GL (i), at low doses, selectively inhibits protein phosphorylation by Kinase P, but has not significant effects on the activities of other kinases (Kinase A, Kinase C and histone kinase); (ii) binds directly to Kinase P and reduces kinase activity in a dose-dependent manner; and (iii) inhibits vesicular stomatitis virus (VSV)-associated kinase activity. These observations strongly suggest that direct binding of GL to the virus causes the direct inactivation of virus-associated kinase and the reduction of the viral infectivity.

Capsid↗
PubMed1997

Low temperature perception in plants: effects of cold on protein phosphorylation in cell-free extracts.

Activities of prevalent protein phosphatases decreased by nearly 95% and those of individual protein kinases were differentially reduced at low temperature. Inhibition of phosphatase activity at temperatures below 12 degrees C resulted in marked hyperphosphorylation of a 58-kDa protein (PP58). The temperature threshold for hyperphosphorylation of PP58 coincided with the known threshold for cold-induced calcium influx. Since calcium influx is triggered by several environmental stresses, we propose that the observed direct effects of cold on the phosphorylation of specific proteins enable cells to couple a shared calcium signal to a cold-specific transduction pathway.

Adenosine Triphosphate↗
PubMed1991

Multiple forms of maturation-promoting factor in unfertilized Xenopus eggs.

Maturation-promoting factor (MPF), which is functionally defined by its ability to induce frog oocyte maturation independent of protein synthesis, is hypothesized to be the mitotic inducer in eukaryotic cells. Previous studies have demonstrated that the cdc2 protein kinase complex (p34cdc2-cyclin) meets the criteria for MPF. In the present study, we show that MPF activity in extracts of unfertilized Xenopus eggs can be resolved into three fractions by Q-Sepharose chromatography. Of the total MPF activity recovered, approximately 20% was in the flow-through fraction that was accounted for by the cdc2 kinase complex, approximately 40% was in the 0.2 M NaCl eluate, and the remaining approximately 40% was in the 0.5 M NaCl eluate. Neither eluate contained cdc2 kinase, but each could activate cdc2 kinase upon microinjection into Xenopus oocytes. The MPF activity in the two eluates, but not in the flow-through fraction, could be depleted by the mitosis-specific monoclonal antibody MPM-2. This antibody has been shown to inhibit Xenopus oocyte maturation and deplete MPF activity from mature oocyte extract but does not recognize the cdc2 kinase complex. The three MPFs differed in apparent molecular size, H1 kinase activity, and stability at 4 degrees C. We propose that MPF activity in unfertilized Xenopus eggs resides in at least three different molecular species, the combined activities of which may be required for autoamplification of MPF.

Amino Acid Sequence↗
PubMed1991

Cell cycle regulation of histone H1 kinase activity associated with the adenoviral protein E1A.

Several cellular proteins form stable complexes with the proteins encoded by the adenovirus early region 1A (E1A) gene in extracts derived from adenovirus infected or transformed cells. Two of the cellular proteins that bind to E1A have been identified; one, a 105-kilodalton protein (pRb), is the product of the retinoblastoma gene, and the other, a 60-kilodalton protein, is a human cyclin A. Two other proteins that bind E1A have now been shown to be related to p34cdc2. This E1A complex displayed histone H1-specific kinase activity; the kinase activity was modulated during the cell division cycle, and association of pRb with E1A apparently was not required for this activity.

Adenovirus Early Proteins↗
PubMed1977

Studies on the cyclic 3':5'-AMP-stimulated pig liver protein kinase reaction with pyruvate kinase as substrate.

The phosphorylation of pig liver pyruvate kinase by cyclic adenosine 3':5'-monophosphate-dependent protein kinase has been studied. For comparison, mixed histone and a synthetic heptapeptide were also used as substrates. Protein kinase was purified by chromatography on DEAE-cellulose, hydroxyapatite, and Sephadex G-200. The enzyme was stimulated by cyclic AMP with apparent Ka values of 2.5 and 0.8 x 10-7 M for pyruvate kinase and histone substrates, respectively. Divalent cations were essential for the activity of the protein kinase. Variation of the concentration of ATP resulted in approximately straight lines in Lineweaver-Burk plots for the phosphorylation of both pyruvate kinase and mixed histone. The apparent Km values for ATP were 21 and 11 muM, respectively. The phosphorylation rate increased with the concentration of pyruvate kinase even at a concentration of 2 muM pyruvate kinase. At a high ionic strength, the phosphorylation rate of both pyruvate kinase and histone decreased. The phosphorylation rate varied markedly with pH in imidazole/HC1 and Tris/HC1 buffers. At slightly alkaline pH values, pyruvate kinase was phosphorylated at a much higher rate than pH7, but this was not the case for histone. At pH 8.5, the phosphorylation rate of pyruvate kinase was 3.5 times the rate at pH 7, while the corresponding increase for the histone phosphorylation was 50 per cent. In potassium phosphate buffers, the phosphorylation rate of both substrates did not change significantly over the pH range studied. Arrhenius' plots of the protein kinase reaction resulted in a break at about 10 degrees when pyruvate kinase was used as substrate, whereas a straight line was obtained when using histone. The negative allosteric effectors of pyruvate kinase, alanine, and phenylalanine, increased the phosphorylation rate of pyruvate kinase at pH 8 by 50 and 120 per cent, respectively. The same effectors did not influence the phosphorylation rate of mixed histone or a synthetic heptapeptide. It is concluded that the conformations adopted by pyruvate kinase in the presence of allosteric inhibitors make it a better substrate for the protein kinase.

Adenosine Triphosphate↗
PubMed1976

Studies on the sites in histones phosphorylated by adenosine 3':5'-monophosphate-dependent and guanosine 3':5'-monophosphate-dependent protein kinases.

Adenosine 3':5'-monophosphate-dependent protein kinase (protein kinase A) purified from silkworm pupae phosphorylated five major fractions of calf thymus histone, whereas guanosine 3':5'-monophosphate-dependent protein kinase (protein kinase G) purified from the same organism reacted preferentially with H1, H2A, and H2B histones. Amino acid analysis of the phosphopeptides which were obtained by proteolytic digestion revealed that both protein kinases A and G showed the abilities to phosphorylate the same serine hydroxyl groups in H1 and H2B histones. Both protein kinases reacted with Ser-38 in H1 histone. With H2B histone as substrate protein kinase A phosphorylated Ser-32 as well as Ser-36, whereas protein kinase G reacted preferentially with Ser-32 and the reaction with Ser-36 was very slow. H3 and H4 histones were practically inactive substrates for protein kinase G. Although H2A histone has not been analyzed, the evidence has raised a possibility that protein kinase G utilizes a portion of the substrate proteins for protein kinase A.

Amino Acids↗
PubMed1996

Candida albicans CDK1 and CYB1: cDNA homologues of the cdc2/CDC28 and cdc13/CLB1/CLB2 cell cycle control genes.

Major transitions in the eukaryotic cell cycle are regulated by the cyclin-dependent protein kinases (CDK). In particular, the G2/M transition is initiated by the activity of a complex formed by a CDK of the Cdc2/Cdc28 family and B-type cyclins of the Cdc13/C1b family in the yeasts, Schizosaccharomyces pombe (Sp) and Saccharomyces cerevisiae (Sc). To study the molecular mechanisms that control the G2/M transition in the dimorphic pathogenic yeast, Candida albicans, we have cloned and characterized cDNAs corresponding to CDK1 and CYB1. The CDK1 cDNA encodes a 317-amino-acid (aa) protein that shares 76.8 and 62.3% identity with the Sc CDC28 and Sp cdc2 gene products, respectively. The CYB1 cDNA encodes a 493-aa protein that is 34.8, 34.4 and 35.5% identical to Sc C1b1 and C1b2, and to Sp Cdc13, respectively. Cyb1 contains characteristic mitotic destruction and cyclin boxes. The CDK1 and CYB1 cDNAs are functional homologues, as they are able to complement Sp cdc2 and cdc13 temperature-sensitive (ts) mutations, respectively, and their gene products interact in vivo in Sc to form an active histone H1 kinase.

Amino Acid Sequence↗
PubMed1989

Dephosphorylation and activation of Xenopus p34cdc2 protein kinase during the cell cycle.

Genetic studies in the fission yeast Schizosaccharomyces pombe have established that a critical element required for the G2----M-phase transition in the cell cycle is encoded by the cdc2+ gene. The product of this gene is a serine/threonine protein kinase, designated p34cdc, that is highly conserved functionally from yeast to man2 and has a relative molecular mass of 34,000 (34 K). Purified maturation-promoting factor (MPF) is a complex of p34cdc2 and a 45K substrate that appears in late G2 phase and is sufficient to drive cells into mitosis. This factor has been identified in all eukaryotic cells, and in vitro histone H1 is the preferred substrate for phosphorylation. The increase in the activity of H1 kinase in M-phase is associated with a large increase in total cell protein phosphorylation which is believed to be a consequence of MPF activation. We show here that the H1 kinase activity of p34cdc2 oscillates during the cell cycle in Xenopus, and maximal activity correlates with the dephosphorylated state of p34cdc2. Direct inactivation of MPF in vitro is accompanied by phosphorylation of p34cdc2 and reduction of its protein kinase activity.

Animals↗
PubMed1989

M phase-promoting factor: its identification as the M phase-specific H1 histone kinase and its activation by dephosphorylation.

A major protein kinase independent of Ca2+, cyclic nucleotide or diacylglycerol, the activity of which becomes maximal when cells enter M phase, decreases at ana-telophase, and is low during interphase, has been purified to near homogeneity from starfish oocytes and its catalytic subunit identified as p34cdc2. M phase-promoting factor (MPF) was found to co-purify with the M phase-specific kinase throughout its purification. p34cdc2 does not have to be associated with any specific protein for expression of H1 histone kinase or MPF activities. When p34cdc2 is phosphorylated its protein kinase activity is inhibited, preventing entry into M phase, but once p34cdc2 becomes dephosphorylated, its protein kinase activity increases and M phase is initiated. A second peak of MPF activity was separated from p34cdc2 in the ammonium sulfate fraction treated with ATP-gamma-S. It induced p34cdc2 dephosphorylation and the concomitant stimulation of its kinase activity when injected in Xenopus or starfish oocytes.

Adenosine Triphosphate↗
PubMed1977

[Isolation and some properties of protein kinase from pigeon breast muscle].

Protein kinase was isolated from pigeon breast muscle. The preparation obtained was chromatographically homogeneous. The apparent Km varlue for histone H1 and ATP were 3,5-10(-5) M and 1,6-10(-5) M respectively. The purified enzyme displays high specificity for the lysine-rich histones (H1, H2b, H2a). The protein kinase activity is stimulated, 1,6-fold by cyclic AMP.

Animals↗