To study a cyclin-dependent kinase (CDK) from alfalfa (Medicago sativa L.), an antibody was raised against the C-terminal 16 amino acids of the protein cdc2aMs. The cdc2Ms protein was immunopurified with this antibody and its histone kinase activity was measured. The cdc2Ms kinase is activated at the G1/S transition when phosphate-starved cells from the G0 phase re-enter the cell cycle and rema...

Myricetin, a naturally occurring flavonol, has been shown to inhibit the proliferation of human hepatoma HepG2 cells and to induce G2/M phase arrest. However, the underlying mechanisms of Myricetin activity have yet to be revealed. The aim of the present study was to clarify the molecular mechanisms of cell cycle arrest induced by myricetin in HepG2 cells. The MTT assay confirmed that exposure ...

Spcl in Schizosaccharomyces pombe is a member of the stress-activated protein kinase family, an evolutionary conserved subfamily of mitogen-activated protein kinases (MAPKs). Spcl is activated by a MAPK kinase homologue, Wisl, and negatively regulated by Pypl and Pyp2 tyrosine phosphatases. Mutations in the spcl ± and wisl genes cause a G2 cell cycle delay that is exacerbated during stress. Her...

Previous work has established that activation of Mos, Mek, and p42 mitogen-activated protein (MAP) kinase can trigger release from G2-phase arrest in Xenopus oocytes and oocyte extracts and can cause Xenopus embryos and extracts to arrest in mitosis. Herein we have found that activation of the MAP kinase cascade can also bring about an interphase arrest in cycling extracts. Activation of the ca...

the hydrophobic proteins of plant plasma membrane still remain largely unknown.  for example in the arabidopsis genome, receptor-like kinases (rlks) are plasma membrane proteins, functioning as the primary receptors in the signaling of stress conditions, hormones and the presence of pathogens form a diverse family of over 610 genes. a limited number of these proteins have appeard in protein pro...

The S-M checkpoint ensures that entry into mitosis is dependent on completion of DNA replication. In the fission yeast Schizosaccharomyces pombe, the SM checkpoint mutant cdc2-3w is thought to be defective in receiving the checkpoint signal. To isolate genes that function in the checkpoint pathway, we screened an S. pombe cDNA library for genes that, when overexpressed, could suppress the check...

we have investigated the effect of theophylline on the kinetics of the catalytic subunit of protein kinase and related factors in lung tissue. the results show that the point of highest concentration of the c subunit of protein kinase which is active in casein phosphorylation is at 3h of incubation time, but in the presence of 100 ilg/ inl and 10µg/ml theophylline, this is shifted to i.s and 2....

Lymphocytes isolated from human immunodeficiency virus (HIV)-infected patients have dysregulated cell-cycle control, consisting of increased activation of the cyclin B1/p34 cdc2 complex and abnormal nucleolar structure. To better characterize the molecular features of the HIV-associated cell-cycle perturbations, we performed a detailed analysis of the posttranslational regulation of nucleolin, ...

Figure 1: In step 1, cyclin is synthesized de novo. Newly synthesized cyclin may be unstable (step 2). Cyclin combines with cdc2-P (step 3) to form pre-maturation promoting factor (preMPF). At some point after heterodimer formation, the cyclin subunit is phosphorylated. ... The cdc2 subunit is then dephosphorylated (step 4) to form active MPF. In principle, the activation of MPF may be opposed ...