Gert Rijksen

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Polo-like kinases (PLKs) have an important role in several stages of mitosis. They contribute to the activation of cyclin B/Cdc2 and are involved in centrosome maturation and bipolar spindle formation at the onset of mitosis. PLKs also control mitotic exit by regulating the anaphase-promoting complex (APC) and have been implicated in the temporal and(More)
The cyclin-dependent kinase inhibitor p21 is required for a sustained G(2) arrest after activation of the DNA damage checkpoint. Here we have addressed the mechanism by which p21 can contribute to this arrest in G(2). We show that p21 blocks the activating phosphorylation of Cdc2 on Thr(161). p21 does not interfere with the dephosphorylation of two(More)
Wnt mediated signal transduction is considered to regulate activity of target genes. In Xenopus embryos, ectopic Wnt1 and Wnt8 expression induces gap-junctional communication. During murine brain formation, Wnt1 and the gap-junctional protein connexin43 (Cx43) are co-expressed at the mid/hindbrain border, while interference with Wnt1 or Cx43 expression(More)
Tyrosine phosphorylation is an important regulatory mechanism in response to the action of growth factors and oncogenes. Since many oncogenes code for tyrosine kinases, increased or altered oncogene expression may be reflected in increased tyrosine kinase activity. In a recent study (Hennipman et al., Cancer Res., 49: 516-521, 1989), we found that the(More)
p21waf1 has been shown to mediate the p53-dependent growth arrest induced by DNA-damaging agents. Several functions have been ascribed to p21waf1 that could be involved in this growth arrest. For one, p21waf1 is an efficient inhibitor of cyclin-dependent kinases (CDKs). Also, p21waf1 can interact with proliferating cell nuclear antigen (PCNA), and as such(More)
This study reports the isolation and characterization of a variant of the human CCRF-CEM leukemia cell line that overproduces the carrier protein responsible for the uptake of reduced folates and the folate analogue methotrexate. The variant was obtained by adapting CCRF-CEM cells for prolonged times to stepwise decreasing concentrations of(More)
To study the relationship between the tyrosine kinase c-Src and the epidermal growth factor receptor (EGF-R), we used the breast cancer cell line ZR75-1, which was transfected with the EGF-R. The EGF-R transfected cell line expressed 60 times more EGF-R than a control cell line transfected with the empty vector. In the presence of EGF, the EGF-R(More)
L1210-B73 cells, variants of L1210 cells grown in medium containing nanomolar concentrations of folates, express a membrane associated folate binding protein (mFBP) in addition to the classical reduced folate/methotrexate carrier (RF/MTX-carrier) present in L1210 cells grown in standard high folate medium (G. Jansen et al., Cancer Res., 49: 1959-1963,(More)
Pyruvate kinase isozymes were studied in normal brain tissue (both fetal and adult) and in meningiomas and malignant gliomas. In fetal brain five different forms could be detected by electrophoresis (K4, K3M, K2M2, KM3, and M4). In adult brain the M4-type, K3M hybrid, and K4-type are present; the M isozyme is largely predominant. Alanine inhibition of(More)
N10-Propargyl-5,8-dideazafolic acid (CB3717) and 2-desamino-2-methyl-N10-propargyl-5,8-dideazafolic acid (ICI-198,583) are potent folate-based inhibitors of thymidylate synthase. We studied the membrane transport and the growth-inhibitory effects of the two thymidylate synthase inhibitors on human CCRF-CEM leukemia cells with different transport properties(More)